Electron injection from the side of an M-DNA duplex

Photoluminescence quenching/recovery kinetics of [Ru(bpy)2(tatp)]2+ and [Ru(bpy)2(dmtatp)]2+ intercalated within DNA by copper(II) ions and EDTA

The quenching and recovery kinetics of photoluminescence of [Ru(bpy)(2)(tatp)](2+) (Ru1) and [Ru(bpy)(2)(dmtatp)](2+) (Ru2) intercalated within DNA (where bpy=2,2'-bipyridine, tatp=1,4,8,9-tetra-aza-triphenylene and dmtatp=2,3-dimethyl-1,4,8,9-tetra-aza-triphenylene) have been investigated by steady-state and time-resolved methods performed at various temperatures (293-333K). Two complexes Ru1 and Ru2 show a single-exponential luminescence decay with τ(Ru1)=246.0 ns and τ(Ru2)=513.5 ns, whose luminescence upon intercalating into DNA exhibits very consistent bi-exponential decay changes. The addition of Cu(2+) ions is found to dynamically quench the luminescence of both DNA-bound Ru(II) complexes, involving a spontaneous exothermic process. The sequential addition of EDTA can partially recover the luminescence quenched by Cu(2+), however depending on methyl substituents of the intercalative ligand. The chemical conversion and luminescence control mechanism of the two DNA-bound Ru(II) complexes is discussed in detail. The present results should be of value for better understanding chemical modulation of DNA-bound Ru(II) complexes as luminescence probes.

Effects of Metal Ions on Conductivity and Structure of Single DNA Molecule in Different Environmental Conditions

We design a novel nano-gap electrode to measure the current of DNA molecule, by which the current-voltage characteristics of individual native DNA, Ag-DNA and Ni-DNA molecules are obtained, respectively. The results show that the voltage gap of Ag- and Ni-DNA is higher than that of native DNA, and the conductance is lower than native DNA in neutral environment. The structure transition from B- to Z-DNA is observed in the presence of high concentrations of nickel ions and Ag-DNA appears chaos state by STM image and U-V spectra characterization. But in alkaline environment, the conductance of Ni-DNA rises and the voltage gap decreases with the increasing of nickel ion concentration denotes that the conductive ability of Ni-DNA is higher than that of native DNA.

Length-dependent conductance of molecular wires and contact resistance in metal-molecule-metal junctions

Molecular wires are covalently bonded to gold electrodes--to form metal-molecule-metal junctions--by functionalizing each end with a -SH group. The conductance of a wide variety of molecular junctions is studied theoretically by using first-principles density functional theory (DFT) combined with the nonequilibrium Green's function (NEGF) formalism. Based on the chain-length-dependent conductance of the series of molecular wires, the attenuation factor beta is obtained and compared with the experimental data. The beta value is quantitatively correlated to the molecular HOMO-LUMO gap. Coupling between the metallic electrode and the molecular bridge plays an important role in electron transport. A contact resistance of 6.0+/-2.0 Kohms is obtained by extrapolating the molecular-bridge length to zero. This value is of the same magnitude as the quantum resistance.

A metallo base-pair incorporating a terpyridyl-like motif: bipyridyl-pyrimidinone.Ag(I).4-pyridine

The design and characterization of a geometrically unique, metallo base-pair motif is reported.