A Photo-responsive Transmembrane Anion Transporter Relay

Abstract

Ion transport across lipid membranes in biology is controlled by stimuli-responsive membrane channels and molecular machine ion pumps such as ATPases. Here, we report a synthetic molecular machine-like ion transport relay, in which transporters on opposite sides of a lipid bilayer membrane facilitate transport by passing ions between them. By incorporating a photo-responsive telescopic arm into the relay design, this process is reversibly controlled in response to irradiation with blue and green light. Transport occurs only in the extended state when the length of the arm is sufficient to pass the anion between transporters located on opposite sides of the membrane. In contrast, the contracted state of the telescopic arm is too short to mediate effective transport. The system acts as a stimuli-responsive ensemble of machine-like components, reminiscent of robotic arms in a factory assembly line, working cooperatively to mediate ion transport. This work points to new prospects for using lipid bilayer membranes as scaffolds for confining, orientating, and controlling the relative positions of molecular machines, thus enabling multiple components to work in concert and opening up new applications in biological contexts.

Controlling transmembrane ion transport via photo-regulated carrier mobility

“…However, in these photo-switchable systems the OFF isomers typically have some background transport activity because they can inevitably bind anions to some extent. Azobenzene switching has also been used to regulate transport via a relay mechanism 22 and to control a membrane-spanning [2]rotaxane. 23 Irreversible redox modulation of anion binding affinity and therefore transport activity has also been reported for chalcogen bonding anionophores.…”

Progress and prospects toward supramolecular bioactive ion transporters

“…Recently, highly selective methods, including stimuli-responsive protransporters, have been developed by several research groups including us to achieve control over the locus of action of the anionophores. 61,79,85,[87][88][89][90][91][92][93][94][95][96][97][98][99][100] Taken together, synthetic ion transport systems undoubtedly possess immense potential to be used as therapeutic agents in curing life-threatening diseases like cystic fibrosis and cancer. This field has grown rapidly, and new systems with improved efficiencies have recently been reported.…”

Molecular Machines and Microrobots: Nanoarchitectonics Developments and On-Water Performances

“…Langton and co-workers demonstrated that an artificial ion transporter on the opposite side of a lipid bilayer can serve as a molecular machine-like ion transport relay ( Figure 9 ) [ 136 ]. The transporter incorporates a photo-responsive stretchable arm that can be reversibly controlled in response to exposure to blue and green light.…”

“… Artificial ion transporter on the opposite side of a lipid bilayer can serve as a molecular machine-like ion transport relay using a photo-responsive stretchable arm. Reproduced under terms of the CC-BY license [ 136 ]. …”