Biology Reference
In-Depth Information
Figure 7.14.
Schematic diagram of SECM measurement of electron
transfer through DNA duplexes that allowed to provided a possible
mechanism for the differences in charger transfer resistances before and
afterZn
2
+
additiontodsDNAfilms.B.Liu,A.J.Bard,C.-Z.LiandH.-B.Kraatz
J. Phys. Chem. B
2005,
109
, 5193-5198. Copyright 2005 American Chemical
Society.
the redox probe into the film and are sensitive not only to the
presence or absence of a single nucleotide mismatch but also to
its position. Figure 7.15 shows measurements with mismatches in
three different positions within the ds-DNA. All three systems give
a distinct amperometric response, which was amplified after the
addition of Zn
2
+
. Moreover, impedimetric study also corroborates
the SECM results [96]. Recently, SECM has shown strong potential
towards the application for species identification [97, 98].
Recently, the effects of various metal ions on the electrochemical
impedance spectra of 25-mer dsDNA films were reported. These
metal ions include Mg
2
+
and Ca
2
+
, known to have high a
nity for
the phosphate backbone of DNA, the trivalent Al
3
+
and La
3
+
,and
divalenttransitionmetalionsNi
2
+
,Cu
2
+
,Zn
2
+
,Cd
2
+
andHg
2
+
.Inall
cases, the presence of metal ions decreases the
R
ct
of ds-DNA films,
presumably due to their coordination with the backbone phosphate
and potentially association with one or more of the exocyclic
