Triggered Reversible Reconfiguration of G-Quadruplex-Bridged "Domino"-Type Origami Dimers: Application of the Systems for Programmed Catalysis.

The reversible and switchable reconfiguration of the two-origami-dimer mixture AB plus CD into the dimer mixture DA plus BC and back using the triggered formation of K-ion-stabilized G-quadruplexes and subsequent treatment with 18-crown-6-ether is presented. The reconfiguration processes are followed by atomic force microscopy imaging of the dimer structures that include tiles marked with 0, 1, 2, and 3 4× hairpin labels. By the functionalization of AB and CD dimers with the Mg-ion-dependent DNAzyme subunits, the AB plus CD mixture leads to the cleavage of the fluorophore- and quencher-modified substrate of the DNAzyme and to the activation of the fluorescence of the fluorophore (fluorescein)-modified fragment product. The K-ion-induced isomerization of the mixture of AB plus CD into the mixture DA plus BC separates the Mg-ion-dependent DNAzyme subunits and concomitantly reconfigures the K-ion-stabilized G-quadruplex associated with the two dimers. After the binding of hemin to the G-quadruplexes, the hemin/G-quadruplex DNAzyme is generated, leading to the catalyzed oxidation of Amplex Red by HO to yield the fluorescent resorufin product. By the cyclic treatment of the AB plus CD mixture with K ions to yield the DA plus BC mixture and the subsequent recovery of the AB plus CD mixture by subjecting the DA plus BC mixture to 18-crown-6-ether, the fluorescence output signals of the system are switched on and off between the fluorescence of fluorescein and resorufin, respectively.