Biomedical Engineering Reference
In-Depth Information
2.4
3
2.2
2.9
2
2.8
1.8
2.7
1.6
2.6
1.4
1.2
2.5
1
2 3 4
Target DNA concentration (micromole)
5
1
2 3 4
Target DNA concentration (micromole)
5
B
Figure 11.15
Increase in (a) the fractal dimension, D f1 and (b) the fractal dimension, D f2 with an increase in the
target DNA concentration (in
A
m
M) in solution.
The fit is reasonable. There is scatter in the data. Only three data points are available. The
availability of more data points would lead to a more reliable fit. The fractal dimension,
D f1 , exhibits only a very mild (equal to 0.349) order of dependence on the target DNA con-
centration in solution in the 1-5 m M range.
Figure 11.15b and Tables 11.7 and 11.8 show the increase in the fractal dimension, D f2 , with
an increase in the target DNA concentration in solution in the 1-5 m M range. For the data
shown in Figure 11.15b the fractal dimension, D f2 , is given by:
0
:
103
0064
D f1 ¼ð
2
:
539
0
:
115
Þ½
target DNA, in m M
ð
11
:
7e
Þ
The fit is reasonable. There is scatter in the data. Only three data points are available. The
availability of more data points would lead to a more reliable fit. The fractal dimension,
D f2 , exhibits only a very low (equal to 0.103) order of dependence on the target DNA con-
centration in solution in the 1-5 m M range. Note that the fractal dimension is based on a
log scale, and even small changes in the fractal dimension lead to significant changes in
the degree of heterogeneity on the sensor chip surface.
Blair et al. (2007 ) report that techniques have been used for the in situ quantification of DNA
during enzymatic synthesis, for example, during a real-time polymerase chain reaction
( Watzinger et al., 2006 ). Blair et al. (2007) point out that hybridization probes involving
“molecular beacons” is a DNA quantification method. They have a stem-loop structure with
complementary ends that anneal to each other. A fluorophore and a quencher are at opposite
ends. Blair et al. (2007) explain that the loop structure is complementary to the target. Thus,
as the beacon binds to the target, the fluorophore is separated from the quencher. This leads
to an increase in the fluorescence, and is proportional to the amount of the DNA produced
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