A Light‐Operated Molecular Cable Car for Gated Ion Transport

Abstract

Inspired by the nontrivial and controlled movements of molecular machines, we report an azobenzene‐based molecular shuttle PR2, which can perform light‐gated ion transport across lipid membranes. The amphiphilicity and membrane‐spanning molecular length enable PR2 to insert into the bilayer membrane and efficiently transport K+ (EC50=4.1 μm) through the thermally driven stochastic shuttle motion of the crown ether ring along the axle. The significant difference in shuttling rate between trans‐PR2 and cis‐PR2 induced by molecular isomerization enables a light‐gated ion transport, i.e., ON/OFF in situ regulation of transport activity and single‐channel current. This work represents an example of using a photoswitchable molecular machine to realize gated ion transport, which demonstrates the value of molecular machines functioning in biomembranes.

Light-Driven Molecular Motors Boost the Selective Transport of Alkali Metal Ions through Phospholipid Bilayers

“…The selective transport of ions across lipid bilayers is a key process to ensure the integrity of living cells and to provide them with advanced functionalities. − If simple biomolecular carriers are processed by a passive mode of transport, more sophisticated protein channels can involve channel-based regulation mechanisms (or even active transport) using external effectors (or a source of energy). Beyond natural ion channels, synthetic artificial pores, with a few including shuttling molecular machines, − have demonstrated remarkable applicative interests for sensing, separation, and delivery processes. − In particular, light-controlled molecular systems offer the opportunity to govern, under temporal and spatial control, a large number of ionic translocation processes through bilayer membranes. , Light-gated photochromic ligands have been designed to change the pore diameter or the ion–dipole action of both protein and artificial channels. Light-regulated carriers or channels − with individual ion-conduction states in bilayer membranes can be optically switched between different states via the photoisomerization of their former components.…”

Recent Progress in Light-Driven Molecular Shuttles

“…An artificial pH-driven molecular shuttle operating in lipid bilayers for ion transport has been reported, but the gated ion transport is not implemented (Chen et al, 2018). Inspired by the working mechanism of Channelrhodopsins (ChRs), Wang et al (2021) designed a light-driven molecular shuttle ([2]rotaxane 37, Figure 13) with an attractive light-gated ion transport behavior.…”

Photochemical Energy Conversion with Artificial Molecular Machines

“… 73 , 74 Such an endeavour can take significant advantage from the approaches pursued in the making of artificial molecular machines. 75 − 77 …”

“…Conversely, passive transporters simply facilitate the system to relax to equilibrium by moving a cargo down a concentration gradient. The controlled transport of molecular and ionic substrates across biological membranes, that define and separate compartments, is a fundamental task for living organisms. − The construction of artificial molecular species capable of performing such a function is motivated not only by the high basic science value but also by the potential for technological and medical applications. , Such an endeavour can take significant advantage from the approaches pursued in the making of artificial molecular machines. − …”