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.
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