Rational design of metal-responsive functional DNA supramolecules

Abstract

DNA molecules have excellent molecular recognition abilities through the complementary hydrogen-bonded base pairing. Since the hybridization of oligonucleotides can be programmed based on the sequences of the nucleobases, a great number of DNA supramolecular architectures have been constructed via self-assembly processes. The development of stimuli-responsive DNA supramolecules has attracted increasing interests because it will contribute to the construction of dynamic molecular systems such as molecular machines. Metal ions are considered as useful chemical stimuli, but the construction of metal-responsive DNA systems is still in the early stage. This review article describes current progress on the development of DNA supramolecules whose structure and function can be regulated in response to metal ions, with mainly focusing on our recent studies. The basic strategy is the introduction of unnatural metal ligands that form interstrand metal complexes in DNA structures. For example, artificial metal-mediated base pairs, formed through complexation between ligand-type nucleobase analogs and a bridging metal ion, were incorporated into known DNAzymes (catalytic DNA) to allosterically regulate their activity in a metal-responsive manner. Novel ligand-type nucleobases that form both metal-mediated and hydrogen-bonded base pairs have been recently devised as metal-responsive building blocks, and were used to construct a simple prototype of DNA molecular machines. Branched DNA structures bearing metal ligands at the junction core were also synthesized as novel structural motifs, with which metal-mediated structure transformation was demonstrated. These metal-responsive DNA supramolecules are expected to expand the toolbox of DNA-based supramolecular chemistry and nanotechnology.