On the role of mercury in the non-covalent stabilisation of consecutive U-Hg^II-U metal-mediated nucleic acid base pairs: Metallophilic attraction enters the world of nucleic acids

Metal atoms with a closed-shell electronic structure and positive charge as for example the Au^I, Pt^II, Ag^I, Tl^I or Hg^II atoms do not in some compounds repel each other due to the so-called metallophilic attraction (P. Pyykkö, Chem. Rev., 1997, 97, 597-636). Here we highlight the role of the Hg^II⋯Hg ^II metallophilic attraction between the consecutive metal-mediated mismatched base pairs of nucleic acids. Usually, the base stacking dominates the non-covalent interactions between steps of native nucleic acids. In the presence of metal-mediated base pairs these non-covalent interactions are enriched by the metal-base interactions and the metallophilic attraction. The two interactions arising due to the metal linkage of the mismatches were found in this study to have a stabilizing effect on nucleic acid structure. The calculated data are consistent with recent experimental observations. The stabilization due to the metallophilic attraction seems to be a generally important concept for the nucleic acids containing heavy metals with short contacts.