Formation of supramolecular channels by reversible unwinding-rewinding of bis(indole) double helix via ion coordination

Abstract

Stimulus-responsive reversible transformation between two structural conformers is an essential process in many biological systems. An example of such a process is the conversion of amyloid-β peptide into β-sheet-rich oligomers, which leads to the accumulation of insoluble amyloid in the brain, in Alzheimer’s disease. To reverse this unique structural shift and prevent amyloid accumulation, β-sheet breakers are used. Herein, we report a series of bis(indole)-based biofunctional molecules, which form a stable double helix structure in the solid and solution state. In presence of chloride anion, the double helical structure unwinds to form an anion-coordinated supramolecular polymeric channel, which in turn rewinds upon the addition of Ag+ salts. Moreover, the formation of the anion-induced supramolecular ion channel results in efficient ion transport across lipid bilayer membranes with excellent chloride selectivity. This work demonstrates anion-cation-assisted stimulus-responsive unwinding and rewinding of artificial double-helix systems, paving way for smart materials with better biomedical applications.

Stimuli-responsive synthetic helical polymers

“…17a). 174 The foldameranion interaction causes the unwinding of the double helical structure to form an anion-coordinated supramolecular polymeric channel, and where the double helical structure can be recovered by adding Ag + salts (Fig. 17b), demonstrating the reversibility of the process.…”

Progress and prospects toward supramolecular bioactive ion transporters

“…Along these lines, very recently, we introduced the bis(indole)-based receptors 20a–20e (Fig. 12A), which showed a reversible change in the conformational behaviour from double helix structure to Cl − ion-coordinated supramolecular polymeric channel 125 (Fig. 12B).…”

Furazan bis-ureas: a heterocyclic scaffold for anion binding and transport

“…[4][5][6][7][8][9][10][11][12] Anionophoric scaffolds using simple cyclic hydrocarbon or aromatic frameworks have become popular due to their synthetic availability and integral lipophilicity. [13][14][15][16][17][18][19][20] However, increasing the complexity of scaffold design can often be accompanied by long and arduous synthetic pathways. 21 As the field of anion recognition and transmembrane transport progresses towards potential therapeutic applications, there is a growing desire to create effective anionophoric scaffolds that are synthetically accessible.…”