Biomedical Engineering Reference
In-Depth Information
0.2
0.15
0.1
0.05
0
2.1
2.15
2.2 2.25 2.3
Fractal dimension,
D
f2
2.35
2.4
2.45
Figure 16.14
Increase in the binding rate coefficient, k
2
, with an increase in the fractal dimension, D
f2
.
Li et al. (2001)
report that there are phosphate groups on the oligonucleotide. Single strand
DNA will dissociate in solution and process a negative charge. This will hinder the formation
of a duplex for the electrostatic repulsion. They further point out that the presence of cations
in solution could counteract the negative charge on the oligonucleotide and accelerate the
hybridization reaction. Thus, they analyzed the influence of Mg
รพรพ
(MgCl
2
) concentration
(0.1 to 500 mM) on the hybridization of the immobilized MB with its target DNA. They
noted that the hybridization efficiency improved when the ion concentration in solution
was increased.
Figure 16.15a
shows the binding of cDNA to the MB immobilized on the biosensor surface in
the presence of 0.1 mM MgCl
2
. 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 are given in
Table 16.12
. It is of interest
to note that as the fractal dimension increases by a factor of 2.68 from a value of
D
f1
equal to
1.0482 to
D
f2
equal to 2.9105, the binding rate coefficient increases by a factor of 802.2 from
a value of
k
1
equal to 0.000226 to
k
2
equal to 0.1813. The changes in the degree of hetero-
geneity or the fractal dimension on the biosensor surface and in the binding rate coefficient
are in the same direction.
Figure 16.15b
shows the binding of cDNA to the MB immobilized on the biosensor surface
in the presence of 1 mM MgCl
2
. 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 are given in
Table 16.12
.
