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An artificial nucleoside surrogate with 1H-imidazo[ 4,5-f][1,10]phenanthroline (P) acting as an aglycone has been introduced into DNA oligonucleotide duplexes. This nucleoside surrogate can act as a bidentate ligand, and so is useful in the context of metal-mediated base pairs. Several duplexes involving a hetero base pair with an imidazole nucleoside have been investigated. The stability of DNA duplexes incorporating the respective AgI-mediated base pairs strongly depends on the sequence context. Quantum mechanical/ molecular mechanical (QM/MM) calculations have been performed in order to gain insight into the factors determining this sequence dependence. The results indicated that, in addition to the stabilizing effect that results from the formation of coordinative bonds, destabilizing effects may occur when the artificial base pair does not fit optimally into the surrounding B-DNA duplex. [ABSTRACT FROM AUTHOR]

A GNA (glycol nucleic acid)-based nucleoside analogue containing 1 H-imidazo[4,5-f][1,10]phenanthroline (P) as an artificial nucleobase was used to form a stable mercury(II)-mediated P-Hg II -T -H base pair within a parallel-stranded DNA duplex. The nucleobase P shows an affinity towards silver(I) and mercury(II), tuneable through the acidity of the medium when the canonical nucleobase thymine is located in its complementary position. This extraordinary behavior was exploited to enable the concomitant site-specific incorporation of silver(I) and mercury(II) into a DNA scaffold for the first time. This achievement is all the more remarkable because it was made possible by the involvement of only one type of artificial nucleobase. The simultaneous incorporation of two different soft metal ions with a precise control of their respective positions within the nucleic acid scaffold significantly reduces the complexity in the formation of a heterometallic array of metal ions in DNA and thereby facilitates new applications of metal-functionalized nucleic acids., (© 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

A GNA (glycol nucleic acid) functionalized nucleoside analogue containing the artificial nucleobase 1H-imidazo[4,5-f][1,10]phenanthroline (P) was used to form a copper(I)-mediated base pair within a DNA duplex. The geometrical constraints imposed by the artificial nucleobase play a pivotal role in this unprecedented stabilization of copper(I) in aqueous medium via metal-mediated base pairing. The formation of the copper(I)-mediated base pair was investigated by temperature-dependent UV spectroscopy and CD spectroscopy. The metal-mediated base pair stabilizes the DNA oligonucleotide duplex by 23 °C. A redox chemistry approach confirmed that this base pair formation was due to the incorporation of copper(I) into the duplex. This first report of a copper(I)-mediated base pair adds metal-based diversity to the field and consequently opens up the range of possible applications of metal-modified nucleic acids., (© 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The investigation of metal-mediated base pairs and the development of their applications represent a prominent area of research at the border of bioinorganic chemistry and supramolecular coordination chemistry. In metal-mediated base pairs, the complementary nucleobases in a nucleic acid duplex are connected by coordinate bonds to an embedded metal ion rather than by hydrogen bonds. Because metal-mediated base pairs facilitate a site-specific introduction of metal-based functionality into nucleic acids, they are ideally suited for use in DNA nanotechnology. This minireview gives an overview of the general requirements that need to be considered when devising a new metal-mediated base pair, both from a conceptual and from an experimental point of view. In addition, it presents selected recent applications of metal-modified nucleic acids to indicate the scope of metal-mediated base pairing., (© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)