Biomedical Engineering Reference
In-Depth Information
Wang et al. (2007)
have recently analyzed esterase 2-ODN conjugates as a sensitive reporter
for the electrochemical detection of nucleic acid hybridization. They wanted to develop
a reporter system consisting of a thermostable enzyme coupled with ODN conjugates for
electrochemical microchip application. They report that the esterase 2 (EST 2) from
Allicyclobacillus acidocaldsrius
is a thermostable monomeric protein.
Figure 13.1a
shows the binding of ODN-P during the hybridization assay with EST 2-A34
reporter (
Wang et al., 2007
). A dual-fractal analysis is required to adequately describe the
binding kinetics. The values of (a) the binding rate coefficient,
k
and the fractal dimension,
D
f
for a single-fractal analysis, and (b) the binding rate coefficients,
k
1
and
k
2
, and the fractal
dimensions,
D
f1
and
D
f2
for a dual-fractal analysis and the dissociation rate coefficient,
k
d
and the fractal dimension,
D
fd
for the dissociation phase for a single-fractal analysis are given
in
Table 13.1(a)
and
13.2(a)
. It is of interest to note that for a dual-fractal analysis, as the
fractal dimension increases from a value of
D
f1
equal 0 to
D
f2
equal to 2.204 the binding rate
coefficient increases by a factor of 56.06 from a value of
k
1
equal to 0.949 to
k
2
equal to
53.15. Note that changes in the fractal dimension or the degree of heterogeneity on the sens-
ing surface and in the binding rate coefficient are in the same direction.
Figure 13.1b
shows the binding of noncomplementary ODN during the hybridization assay
with EST 2-A34 reporter (
Wang et al., 2007
). Once again, a dual-fractal analysis is required
to adequately describe the binding kinetics. The values of (a) the binding rate coefficient,
k
and the fractal dimension,
D
f
for a single-fractal analysis, and (b) the binding rate
coefficients,
k
1
and
k
2
, and the fractal dimensions,
D
f1
and
D
f2
for a dual-fractal analysis
120
25
100
20
80
15
60
10
40
5
20
0
0
0
20
40
Time (s)
60
80
0
20
40
Time (s)
60
80
B
Figure 13.1
Binding of (a) perfectly matched ODN (ODN-P), and (b) the noncomplementary ODN during the
hybridization assay with EST2-A34 reporter (
Wang et al., 2007
). When only a solid line is used then
a single-fractal analysis applies. When both a solid line and a dashed line are used, then the dashed
line is for a single-fractal analysis, and the solid line is for a dual-fractal analysis.
A
