Metal-responsive structural transformation between artificial DNA duplexes and three-way junctions

Metal-responsive structural transformation between DNA duplexes and three-way junction structures was demonstrated utilizing artificial oligonucleotides modified with a 2,2’-bipyridine ligand.

DNA three-way junctions (3WJs) are essential structural motifs for DNA nanoarchitectures and DNA-based materials. We report herein a metal-responsive structural transformation between DNA duplexes and 3WJs using artificial oligonucleotides modified with a 2,2′-bipyridine (bpy) ligand. A mixture of bpy-modified DNA strands and natural complementary strands were self-assembled exclusively into duplexes without any transition metal ions, while they formed 3WJs in the presence of Ni^II ions. This transformation was induced by the formation of an interstrand Ni^II(bpy)₃ complex, which served as a template for the 3WJ assembly. Altering the amount and identity of the metal ion regulated the 3WJ induction efficiency. Removal of the metal using EDTA quantitatively regenerated the duplexes. The metal-dependent structural conversion shown here has many potential applications in the development of stimuli-responsive DNA materials.

Versatile ruthenium complexes based on 2,2′-bipyridine modified peptoids

Helical peptoids bearing 2,2′-bipyridine form ruthenium complexes via intermolecular binding to linear peptoid strands or intramolecular binding to a cyclic scaffold.

Dual stimuli-induced formation of a μ-hydroxido bridged [Zn9L5(μ-OH)6]12+ half-pipe

Low-symmetry metal–organic architectures that feature unusual binding motifs are useful for exploring new modes of guest recognition.

Low-symmetry metal–organic architectures that feature unusual binding motifs are useful for exploring new modes of guest recognition. Such structures remain difficult to create using current rational design principles. One approach to constructing such architectures is to employ ligands with coordination vectors oriented to preclude the formation of simple, low nuclearity molecular assemblies upon complexation to metal ions. Here we report two new supramolecular assemblies generated from such a ligand: a simple metastable [Zn₃L₃]⁶⁺ assembly, which was observed to convert to a more complex [Zn₉L₅(μ-OH)₆]¹²⁺ twisted half-pipe architecture. Two chemically distinct stimuli—an anionic template and a base—must be applied for the conversion to occur. Perchlorate, perrhenate, trifluoromethanesulfonate and 2-naphthalenesulfonate were found to act as competent templates for the [Zn₉L₅(μ-OH)₆]¹²⁺ structure.

A metal-ion-responsive adhesive material via switching of molecular recognition properties

Common adhesives stick to a wide range of materials immediately after they are applied to the surfaces. To prevent indiscriminate sticking, smart adhesive materials that adhere to a specific target surface only under particular conditions are desired. Here we report a polymer hydrogel modified with both β-cyclodextrin (βCD) and 2,2'-bipyridyl (bpy) moieties (βCD-bpy gel) as a functional adhesive material responding to metal ions as chemical stimuli. The adhesive property of βCD-bpy gel based on interfacial molecular recognition is expressed by complexation of metal ions to bpy that controlled dissociation of supramolecular cross-linking of βCD-bpy. Moreover, adhesion of βCD-bpy gel exhibits selectivity on the kinds of metal ions, depending on the efficiency of metal-bpy complexes in cross-linking. Transduction of two independent chemical signals (metal ions and host-guest interactions) is achieved in this adhesion system, which leads to the development of highly orthogonal macroscopic joining of multiple objects.