A Novel DNA Helical Wire Containing HgII‐Mediated T:T and T:G Pairs

Numerous applications of metal‐mediated base pairs (metallo‐base‐pairs) to nucleic acid based nanodevices and genetic code expansion have been extensively studied. Many of these metallo‐base‐pairs are formed in DNA and RNA duplexes containing Watson–Crick base pairs. Recently, a crystal structure of a metal–DNA nanowire with an uninterrupted one‐dimensional silver array was reported. We now report the crystal structure of a novel DNA helical wire containing Hg^II‐mediated T:T and T:G base pairs and water‐mediated C:C base pairs. The Hg‐DNA wire does not contain any Watson–Crick base pairs. Crystals of the Hg‐DNA wire, which is the first DNA wire structure driven by Hg^II ions, were obtained by mixing the short oligonucleotide d(TTTGC) and Hg^II ions. This study demonstrates the potential of metallo‐DNA to form various structural components that can be used for functional nanodevices.     

Using Ylide Functionalization to Stabilize Boron Cations

The metalated ylide YNa [Y=(Ph₃PCSO₂Tol)⁻] was employed as X,L‐donor ligand for the preparation of a series of boron cations. Treatment of the bis‐ylide functionalized borane Y₂BH with different trityl salts or B(C₆F₅)₃ for hydride abstraction readily results in the formation of the bis‐ylide functionalized boron cation [Y−B−Y]⁺ ( 2 ). The high donor capacity of the ylide ligands allowed the isolation of the cationic species and its characterization in solution as well as in solid state. DFT calculations demonstrate that the cation is efficiently stabilized through electrostatic effects as well as π‐donation from the ylide ligands, which results in its high stability. Despite the high stability of 2 [Y−B−Y]⁺ serves as viable source for the preparation of further borenium cations of type Y₂B⁺←LB by addition of Lewis bases such as amines and amides. Primary and secondary amines react to tris(amino)boranes via N−H activation across the B−C bond.     

A DNA Structure Containing AgI‐Mediated G:G and C:C Base Pairs

Metal‐mediated base pairs have been extensively utilized in many research fields, including genetic‐code extension, novel therapeutics development, and nanodevice design. Compared to other cations, Ag^I is more flexible in pairing with natural base pairs. Herein, we present a DNA structure containing two C‐Ag^I‐C pairs and the first reported G‐Ag^I‐G pair in a short 8mer DNA strand. This structure not only provides detailed insight into these Ag^I‐mediated base‐pairing patterns in DNA, but also represents the first nonhelical DNA structure driven by heavy‐metal ions, thus further contributing to the structural diversity of DNA. This unique complex structure is highly sequence‐dependent, thus implying functional potentials as a new DNA aptamer that can bind and recognize silver ions. These results not only advance our understanding of the interactions between Ag^I and nucleobases, but also provide a unique structural component for the rational design of new DNA nanodevices.