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SBM DNA targets were then introduced inside the negative compartment of the
measuring setup. They found the translocation time was less for the PC DNA target
when compared with the SBM DNA target. This result was exactly opposite to
the previous reports using
-HL ion channels [
58
].
They also reported that the flux of the target DNA was lesser in the case of
SBM as compared with perfect complementary DNA probes. The complementary
DNA probe showed higher blockade current, faster translocation, and higher
flux values in contrast to SBM targets. The data in Fig.
5.9
shows translocation
behavior of different molecules.
Iqbal et al. reported the similar results while using nanopores with reduced
diameters. With the reduced diameter of the nanopore, the channel gave better
discrimination between SBM and PC DNA. They noticed no significant changes
in the cases of 1-base-mismatch, 2-base-mismatch, or 3-base-mismatch. They
also mixed both of the targets (PC and SBM) in a ratio of 1:1 before introducing
into the negative compartment of the measuring setup. They reported that
during first 10 min, SBM behavior was prominent. After 40 min, the nanopore
lost its selectivity and PC behavior was prominent. The PC DNA target hybri-
dized with the hairpin loop DNA and transversed at a faster rate and time while
a
2500
2500
2000
2000
1500
1000
1500
500
0
0
50
100
150
200
250
300
1000
I
b
(pA)
500
0
0
100
200
300
400
500
I
b
(pA)
Fig. 5.9 Figure shows the average translocation time
(ms) vs
I
b
(pA) blockage current.
Gray
triangles
show the SBM and
black circles
show PC DNA targets. It clearly depicts the higher
translocation times and lower flux in the case of SBM ss-DNA targets [
1
]. The
circle
in inset shows
the subsequent addition of SBM target again without flushing the older sample. It means that as
all DNA probes are hybridized with PC DNA before introducing SBM DNA, the channel has lost
its selectivity and gives longer translocation time and higher blockade current in case of SBM
DNA also. Reprinted by permission from Macmillan Publishers Ltd: Nature Nanotechnology,
copyright (2007)
t
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