Stable Hg(II)-mediated base pairs with a phenanthroline-derived nucleobase surrogate in antiparallel-stranded DNA

ABSTRACT: Metal-mediated base pairs involving artificial nucleobases have emerged as a promising means for the site-specific functionalization of nucleic acids with metal ions. In this context, a GNA-appended (GNA: glycol nucleic acid) nucleoside analogue containing the artificial nucleobase 1H-imidazo[4,5-f][1,10]phenanthroline (P) has already been applied successfully in a variety of homo- and heteroleptic metal-mediated base pairs, mainly involving Ag(I) ions. Herein, we report a thorough investigation of the Hg(II)-binding properties of P when incorporated into antiparallel-stranded DNA duplexes. The artificial nucleobase P is able to form Hg(II)-mediated homoleptic base pairs of the type P–Hg(II)–P with a [2 + 2] coordination environment. In addition, the heteroleptic P–Hg(II)–T pair was investigated. The addition of a stoichiometric amount of Hg(II) to a duplex comprising either a P:P pair or a P:T pair stabilizes the DNA duplex by 4.3 °C and 14.5 °C, respectively. The P–Hg(II)–T base pair, hence, represents the most stabilizing non-organometallic Hg(II)-mediated base pair reported to date. The formation of the Hg(II)-mediated base pairs was investigated by means of temperature-dependent UV spectroscopy and CD spectroscopy. GRAPHIC ABSTRACT: [Image: see text] ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (10.1007/s00775-020-01788-x) contains supplementary material, which is available to authorized users.