A dinuclear silver(I)-mediated base pair in DNA formed from 1, N 6 -ethenoadenine and thymine

Abstract

The artificial nucleobase 1,N6-ethenoadenine (εA) is shown to form a dinuclear Ag(I)-mediated base pair with a complementary thymine (T) residue in double-helical DNA. The stabilizing effect brought about by the formation of such a metal-mediated base pair amounts to 5–6 °C. It does not depend on the orientation of the base pair within the duplex, i.e. the εA–Ag(I)2–T base pair confers the same stability as the T–Ag(I)2–εA base pair. Circular dichroism studies and temperature-dependent UV spectroscopy were applied to establish the formation of this Ag(I)-mediated base pair. Based on DFT calculations, a base pair configuration is proposed in which one Ag(I) ion is coordinated by εA-N6 and T-O4, whereas the other Ag(I) ion forms coordinate bonds to εA-N7 and T-N3. The computations indicate a short intramolecular Ag⋯Ag contact of 2.87 Å, suggesting that argentophilic interactions may be involved.