Daisy Chain Rotaxanes Made from Interlocked DNA Nanostructures

Cyclodextrin-Based [c2]Daisy Chain Rotaxane Insulating Two Diarylacetylene Cores

A [c2]daisy chain rotaxane with two diarylacetylene cores was efficiently synthesized in 53 % yield by capping a C₂ -symmetric pseudo[2]rotaxane composed of two diarylacetylene-substituted permethylated α-cyclodextrins (PM α-CDs) with aniline stoppers. The maximum absorption wavelength of the [c2]daisy chain rotaxane remained almost unchanged in various solvents, unlike that of the stoppered monomer, indicating that the two independent diarylacetylene cores were insulated from the external environment by the PM α-CDs. Furthermore, the [c2]daisy chain rotaxane exhibited fluorescence emission derived from both diarylacetylene monomers and the excimer, which implies that the [c2]daisy chain structure can undergo contraction and extension. This is the first demonstration of a system in which excimer formation between two π-conjugated molecules within an isolated space can be controlled by the unique motion of a [c2]daisy chain rotaxane.

Interlocked DNA Nanojoints for Reversible Thermal Sensing

The ability to precisely measure and monitor temperature at high resolution at the nanoscale is an important task for better understanding the thermodynamic properties of functional entities at the nanoscale in complex systems, or at the level of a single cell. However, the development of high-resolution and robust thermal nanosensors is challenging. The design, assembly, and characterization of a group of thermal-responsive deoxyribonucleic acid (DNA) joints, consisting of two interlocked double-stranded DNA (dsDNA) rings, is described. The DNA nanojoints reversibly switch between the static and mobile state at different temperatures without a special annealing process. The temperature response range of the DNA nanojoint can be easily tuned by changing the length or the sequence of the hybridized region in its structure, and because of its interlocked structure the temperature response range of the DNA nanojoint is largely unaffected by its own concentration; this contrasts with systems that consist of separated components.

DNA Origami Catenanes Templated by Gold Nanoparticles

Mechanically interlocked molecules have marked a breakthrough in the field of topological chemistry and boosted the vigorous development of molecular machinery. As an archetypal example of the interlocked molecules, catenanes comprise macrocycles that are threaded through one another like links in a chain. Inspired by the transition metal-templated approach of catenanes synthesis, the hierarchical assembly of DNA origami catenanes templated by gold nanoparticles is demonstrated in this work. DNA origami catenanes, which contain two, three or four interlocked rings are successfully created. In particular, the origami rings within the individual catenanes can be set free with respect to one another by releasing the interconnecting gold nanoparticles. This work will set the basis for rich progress toward DNA-based molecular architectures with unique structural programmability and well-defined topology.

DNA Origami Rotaxanes: Tailored Synthesis and Controlled Structure Switching

Mechanically interlocked supramolecular assemblies are appealing building blocks for creating functional nanodevices. Herein, we describe the multistep assembly of large DNA origami rotaxanes that are capable of programmable structural switching. We validated the topology and structural integrity of these rotaxanes by analyzing the intermediate and final products of various assembly routes by electrophoresis and electron microscopy. We further analyzed two structure-switching behaviors of our rotaxanes, which are both mediated by DNA hybridization. In the first mechanism, the translational motion of the macrocycle can be triggered or halted at either terminus. In the second mechanism, the macrocycle can be elongated after completion of the rotaxane assembly, giving rise to a unique structure that is otherwise difficult to access.