A Novel AgI -DNA Rod Comprising a One-Dimensional Array of 11 Silver Ions within a Double Helical Structure.

DNA/RNA duplexes containing metal-ion-mediated base pairs (metallo-base pairs) have potential applications in developing nucleic acid-based nanodevices and genetic code expansion. Many metallo-base pairs are formed within duplexes stabilized by Watson-Crick base pairs. Recently, the crystal structure of an AgI -DNA nanowire with an uninterrupted one-dimensional silver array was determined. Here, we present a new DNA helical wire, the "AgI -DNA rod", containing an uninterrupted array of 11 AgI ions. The AgI -DNA rod consisted of only C-AgI -C, G-AgI -G, G-AgI -5-bromouracil (Br U), and Br U-AgI -Br U metallo base pairs, with no Watson-Crick pairs. The AgI -DNA rods were connected by non-canonical G-G pairs in crystals. Notably, data from our absorbance, circular dichroism, nuclear magnetic resonance, and mass spectrometry analyses suggested that the AgI -DNA rods formed in solution, as well as within crystals.

Crystal structure of a DNA duplex cross-linked by 6-thioguanine-6-thioguanine disulfides: reversible formation and cleavage catalyzed by Cu(ii) ions and glutathione.

Herein, we determined the crystal structure of a DNA duplex containing consecutive 6-thioguanine-6-thioguanine disulfides. The disulfide bonds were reversibly formed and cleaved in the presence of Cu(ii) ions and glutathione. To our knowledge, this is the first reaction in which metal ions efficiently accelerated disulfide bond formation between thio-bases in duplexes.