A Dinuclear Mercury(II)-Mediated Base Pair in DNA

The first dinuclear metal-mediated base pair containing divalent metal ions has been prepared. A combination of the neutral bis(monodentate) purine derivative 1,N-6-ethenoadenine (epsilon A), which preferentially binds two metal ions with a parallel alignment of the N-M bonds, and the canonical nucleobase thymine (T), which readily deprotonates in the presence of Hg-II and thereby partially compensates the charge accumulation due to the two closely spaced divalent metal ions, yields the dinuclear T-Hg-2(II)-epsilon A base pair. This metal-mediated base pair stabilizes the DNA oligonucleotide duplex as shown by an increase of 8 degrees C in its melting temperature. Formation of the base pair was demonstrated by temperature-dependent UV spectroscopy as well as by titration experiments monitored by UV and CD spectroscopy.