posted on 2018-06-25, 00:00authored byRui Campos, László Kékedy-Nagy, Zhe She, Rana Sodhi, Heinz-Bernhard Kraatz, Elena E. Ferapontova
Electrical
properties of DNA critically depend on the way DNA molecules
are integrated within the electronics, particularly on DNA–electrode
immobilization strategies. Here, we show that the rate of electron
transport in DNA duplexes spacer-free tethered to gold via the adenosine
terminal region (a dA10 tag) is enhanced compared to the
hitherto reported DNA–metal electrode tethering chemistries.
The rate of DNA-mediated electron transfer (ET) between the electrode
and methylene blue intercalated into the dA10-tagged DNA
duplex approached 361 s–1 at a ca. half-monolayer
DNA surface coverage ΓDNA (with a linear regression
limit of 670 s–1 at ΓDNA →
0), being 2.7-fold enhanced compared to phosphorothioated dA5* tethering (6-fold for the C6-alkanethiol linker representing
an additional ET barrier). X-ray photoelectron spectroscopy evidenced
dA10 binding to the Au surface via the purine N, whereas
dA5* predominantly coordinated to the surface via sulfur
atoms of phosphothioates. The latter apparently induces the DNA strand
twist in the point of surface attachment affecting the local DNA conformation
and, as a result, decreasing the ET rates through the duplex. Thus,
a spacer-free DNA coupling to electrodes via dA10 tags
thus allows a perspective design of DNA electronic circuits and sensors
with advanced electronic properties and no implication from more expensive,
synthetic linkers.