Direct Conductance Measurement of Individual Metallo-DNA Duplexes within Single-Molecule Break Junctions

A family of "click" nucleosides for metal-mediated base pairing: unravelling the principles of highly stabilizing metal-mediated base pairs

A family of artificial nucleosides has been developed by applying the Cu(I)-catalyzed Huisgen 1,3-dipolar cycloaddition. Starting from 2-deoxy-β-D-glycosyl azide as a common precursor, three bidentate nucleosides have been synthesized. The 1,2,3-triazole involved in all three nucleobases is complemented by 1,2,4-triazole (TriTri), pyrazole (TriPyr), or pyridine (TriPy). Molecular structures of two metal complexes indicate that metal-mediated base pairs of TriPyr may not be fully planar. An investigation of DNA oligonucleotide duplexes comprising the new "click" nucleosides showed that they can bind Ag(I) to form metal-mediated base pairs. In particular the mispair formed from TriPy and the previously established imidazole nucleoside is significantly stabilized in the presence of Ag(I). A comparison of different oligonucleotide sequences allowed the determination of general factors involved in the stabilization of nucleic acids duplexes with metal-mediated base pairs.

Point decoration of silicon nanowires: an approach toward single-molecule electrical detection

Probing interactions of biological systems at the molecular level is of great importance to fundamental biology, diagnosis, and drug discovery. A rational bioassay design of lithographically integrating individual point scattering sites into electrical circuits is capable of realizing real-time, label-free biodetection of influenza H1N1 viruses with single-molecule sensitivity and high selectivity by using silicon nanowires as local reporters in combination with microfluidics. This nanocircuit-based architecture is complementary to more conventional optical techniques, but has the advantages of no bleaching problems and no fluorescent labeling. These advantages offer a promising platform for exploring dynamics of stochastic processes in biological systems and gaining information from genomics to proteomics to improve accurate molecular and even point-of-care clinical diagnosis.

Crystal structure of metallo DNA duplex containing consecutive Watson-Crick-like T-Hg(II)-T base pairs

The metallo DNA duplex containing mercury-mediated T-T base pairs is an attractive biomacromolecular nanomaterial which can be applied to nanodevices such as ion sensors. Reported herein is the first crystal structure of a B-form DNA duplex containing two consecutive T-Hg(II)-T base pairs. The Hg(II) ion occupies the center between two T residues. The N3-Hg(II) bond distance is 2.0 Å. The relatively short Hg(II)-Hg(II) distance (3.3 Å) observed in consecutive T-Hg(II)-T base pairs suggests that the metallophilic attraction could exist between them and may stabilize the B-form double helix. To support this, the DNA duplex is largely distorted and adopts an unusual nonhelical conformation in the absence of Hg(II). The structure of the metallo DNA duplex itself and the Hg(II)-induced structural switching from the nonhelical form to the B-form provide the basis for structure-based design of metal-conjugated nucleic acid nanomaterials.

Structural and magnetic properties of a variety of transition metal incorporated DNA double helices

By using density functional theory calculations, the structural, energetic, magnetic, and optical properties for a variety of transition metal (M = Mn, Fe, Co, Ni and Cu) ions incorporated modified-DNA (M-DNA) double helices has been investigated. The DNA is modified with either hydroxypyridone (H) or bis(salicylaldehyde)ethylenediamine (S-en) metalated bases. We find the formation of extended M-O network leading to the ferromagnetic interactions for the case of H-DNA for all the metal ions. More ordered stacking arrangement was found for S-en-DNA. We calculate the exchange coupling constant (J) considering Heisenberg Hamiltonian for quantitative description of magnetic interactions. The ferromagnetic and antiferromagnetic interactions are obtained by varying different transition metal ions. The extent of the magnetic interaction depends on the number of transition metal ions. Optical profiles show peaks below 2 eV, a clear signature of spin-spin coupling.

Metallo-foldamers with backbone-coordinative oxime peptides: control of secondary structures

Metal-mediated secondary structures of peptide-based foldamers were constructed using artificial backbone-coordinative oxime peptides. Complexation of the peptides with Pd(II) afforded several mononuclear and dinuclear secondary structures such as helices and hairpins as confirmed by single-crystal XRD and NMR analyses.