The activation of a DNAzyme cascade by the cooperative self-assembly of multicomponent nucleic acid structures is suggested as a method for the amplified sensing of DNA, or the specific substrates of aptamers. According to one configuration, the DNA analyte 1 is detected by two tailored nucleic acids 2 and 3 that form a multicomponent supramolecular structure with a ribonucleobase-containing quasi-circular DNA 4, but only upon the concomitant hybridization with 1. The resulting supramolecular nucleic acid structure includes the Mg(2+)-dependent DNAzyme that cleaves the ribonucleobase site of 4. The cleavage of the quasi-circular DNA 4 results in the fragmentation of the supramolecular structure and the release of two horseradish peroxidase (HRP) mimicking units that were incorporated in the blocked quasi-circular DNA 4. The HRP-mimicking DNAzyme catalyzed the oxidation of 2,2'-azino-bis(3-ethylbenzothiazoline)-6-sulfonic acid (ABTS(2-)) by H(2)O(2) to ABTS(*-), and the product provided the colorimetric readout signal for the analyzed DNA. The method enabled the analysis of DNA with a detection limit of 1 x 10(-12) M. Similarly, an analogous DNAzyme cascade was activated by the low-molecular-weight substrates, adenosine triphosphate (ATP) or cocaine. This was induced by the self-assembly of nucleic acids that included fragments of the respective aptamers and the Mg(2+)-dependent DNAzyme. Furthermore, nucleic acids consisting of fragments of the aptamers against ATP or cocaine and fragments of the HRP-mimicking DNAzyme self-assemble, in the presence of the respective substrates, to the active DNAzyme structure that catalyzes the oxidation of ABTS(2-) by H(2)O(2) to form the colored product ABTS(*-). The resulting product provided the readout signal for the recognition events. The cooperative interaction in the formation of the supramolecular nucleic acid assemblies and the activation of the DNAzymes are discussed.

Open sesame: Aptamer-substrate complexes activate the coherent operation of two tweezers that act as a "SET-RESET" logic system. Each tweezer cycles between a fluorescent open state and a closed quenched state (Q = quencher, F = fluorophore) when triggered by adenosine monophosphate (AMP) and adenosine deaminase (AD).

Supramolecular constructs composed of ion-dependent DNAzymes and their substrates were used to develop DNAzyme cascades that enabled the sensitive detection of UO22+ or the activation of logic gate operations. The supramolecular complex between the UO22+-dependent DNAzyme and its substrate leads, in the presence of UO22+, to the cleavage of the substrate and to the release of the HRP-mimicking DNAzyme that enables the optical analysis of UO22+ (detection limit 1 x 10-9 M). Similarly, supramolecular complexes between the Mg2+- and UO22+-dependent DNAzymes and tailored substrates enables the design of the "OR" and "AND" logic gates, using Mg2+ and UO22+ as inputs.

Sesam, öffne dich! Aptamer‐Substrat‐Komplexe aktivieren die kohärente Funktion zweier Pinzettenstrukturen, die als “SET‐RESET”‐Logiksystem wirken. Bei Einwirkung von Adenosinmonophosphat (AMP) und Adenosin‐Desaminase (AD) wechseln die Pinzettenstrukturen jeweils zwischen einem fluoreszierenden offenen und einem gelöschten geschlossenen Zustand (Q=Löscheinheit, F=Fluorophor).

Reconstitution of apo-glucose oxidase on a photoisomerizable-FAD monolayer linked to a Au electrode leads to the photonic wiring of the enzyme with the electrode and to the optical/electrochemical switching of the bioelectrocatalytic functions of the enzyme.