Nucleic acid duplexes with metal-mediated base pairs and their structures

Metal-mediated base pairs represent a topical area of research at the border of bioinorganic chemistry, supramolecular coordination chemistry and DNA nanotechnology. In a metal-mediated base pair, the hydrogen bonds of a canonical base pair are formally replaced by coordinate bonds to one or more metal ions located in the interior of the duplex. These base pairs can be created by using natural pyrimidine or purine nucleosides but may also involve artificial nucleosides. The review gives a survey of experimental nucleic acid structures containing one or more metal-mediated base pairs, including X-ray crystal structures as well as NMR solution structures. Starting with a selection of small-molecule structures involving model nucleobases, the overview is extended to nucleic acids structures with T-Hg(II)-T and C-Ag(I)-C base pairs formed from canonical pyrimidine bases, other metal-mediated base pairs involving natural nucleobases, and fully artificial metal-mediated base pairs. A comparison of the structures obtained under different experimental conditions allows to draw significant conclusions with respect to the conformational flexibility of metal-modified nucleic acids. (C) 2019 Elsevier B.V. All rights reserved.