A dinuclear silver(I)-mediated base pair in DNA formed from 1,N6-ethenoadenine and thymine

Mandal S, Hebenbrock M, Müller J

Abstract

The artificial nucleobase 1,N 6-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 2.87Å, suggesting that argentophilic interactions may be involved.