The single-molecule conductance of DNA was found to increase by over four fold upon intercalation, while the conductance nearly unaltered upon groove-binding. These effects are interpreted on the basis of the electronic interaction of the DNA-binding molecules with the stacked DNA bases.

Herein, we report on the kinetic investigation for the breakdown of single-molecule junctions.

Single-molecule devices attract much interest in the development of nanoscale electronics.A lthough av ariety of functional single molecules for single-molecule electronics have been developed, there still remains the need to implement sophisticated functionalization towardp ractical applications. Given its superior functionality encountered in macroscopic materials,apolymer could be au seful building blocki nt he single-molecule devices.T herefore,amolecular junction composed of polymer has nowb een created. Furthermore,a n automated algorithm was developed to quantitatively analyze the tunneling current through the junction. Quantitative analysis revealed that the polymer junction exhibits ah igher formation probability and longer lifetime than its monomer counterpart. These results suggest that the polymer provides au nique opportunity to design both stable and highly functional molecular devices for nanoelectronics.

The electrical properties of DNA have been extensively investigated within the field of molecular electronics. Previous studies on this topic primarily focused on the transport phenomena in the static structure at thermodynamic equilibria. Consequently, the properties of higher-order structures of DNA and their structural changes associated with the design of single-molecule electronic devices have not been fully studied so far. This stems from the limitation that only extremely short DNA is available for electrical measurements, since the single-molecule conductance decreases sharply with the increase in the molecular length. Here, we report a DNA zipper configuration to form a single-molecule junction. The duplex is accommodated in a nanogap between metal electrodes in a configuration where the duplex is perpendicular to the nanogap axis. Electrical measurements reveal that the single-molecule junction of the 90-mer DNA zipper exhibits high conductance due to the delocalized π system. Moreover, we find an attractive self-restoring capability that the single-molecule junction can be repeatedly formed without full structural breakdown even after electrical failure. The DNA zipping strategy presented here provides a basis for novel designs of single-molecule junctions.

Hybridization of a single DNA molecule on a surface was investigated by electrical conductance measurements. The hybridization efficiency increases with increasing the DNA concentration, in contrast to preceding studies with ensemble studies.

Single-molecule measurements of biomaterials bring novel insights into cellular events. For almost all of these events, post-translational modifications (PTMs), which alter the properties of proteins through their chemical modifications, constitute essential regulatory mechanisms. However, suitable single-molecule methodology to study PTMs is very limited. Here we show single-molecule detection of peptide phosphorylation, an archetypal PTM, based on electrical measurements. We found that the phosphate group stably bridges a nanogap between metal electrodes and exhibited high electrical conductance, which enables specific single-molecule detection of peptide phosphorylation. The present methodology paves the way to single-molecule studies of PTMs, such as single-molecule kinetics for enzymatic modification of proteins as shown here.

We investigated the formation and breaking of single-molecule junctions of two kinds of dithiol molecules by timeresolved tunneling current measurements in a metal nanogap. The resulting current trajectory was statistically analyzed to determine the single-molecule conductance and, more importantly, to reveal the kinetic property of the single-molecular junction. These results suggested that combining a measurement of the single-molecule conductance and statistical analysis is a promising method to uncover the kinetic properties of the single-molecule junction.

We report on a method to measure the electron transport of a single molecular assembly by scanning tunneling microscopy (STM). The STM molecular tip together with a chemically modified substrate was utilized to form an assembly with a single target molecule. This method was successfully applied to a heme peptide to reveal the transport property of a single peptide-containing assembly. The present work opens a way to create functional single molecular devices using biomolecules.