Tunnel conductance of Watson-Crick nucleoside-base pairs from telegraph noise.
The use of tunneling signals to sequence DNA is presently hampered by the small tunnel conductance of a junction spanning an entire DNA molecule. The design of a readout system that uses a shorter tunneling path requires knowledge of the absolute conductance across base pairs. We have exploited the stochastic switching of hydrogen-bonded DNA base-nucleoside pairs trapped in a tunnel junction to determine the conductance of individual molecular pairs. This conductance is found to be sensitive to the geometry of the junction, but a subset of the data appears to come from unstrained molecular pairs. The conductances determined from these pairs are within a factor of two of the predictions of density functional calculations. The experimental data reproduces the counterintuitive theoretical prediction that guanine-deoxycytidine pairs (3 H-bonds) have a smaller conductance than adenine-thymine pairs (2 H-bonds). A bimodal distribution of switching lifetimes shows that both H-bonds and molecule-metal contacts break.
Chang
Shuai
S
Biodesign Institute, Department of Physics, Arizona State University, Tempe, AZ 85287, USA.
He
Jin
J
Lin
Lisha
L
Zhang
Peiming
P
Liang
Feng
F
Young
Michael
M
Huang
Shuo
S
Lindsay
Stuart
S
D020029:Base Pairing / Q000235:genetics*; D001483:Base Sequence; D004247:DNA / Q000737:chemistry* / Q000235:genetics*; D004553:Electric Conductivity; D004563:Electrochemistry / Q000379:methods*; D008969:Molecular Sequence Data; D017422:Sequence Analysis, DNA / Q000379:methods*
D004247:DNA