Biology Reference
In-Depth Information
often involve incorporation of electro-active centers into the ODNs.
For example, it was demonstrated by Barton [32] that double-
helical DNA films on gold surface display a marked sensitivity
to the presence of base mismatches within the immobilized
duplexes. Moreover, it has been observed that mismatch detection
is possible regardless of DNA sequence composition and mismatch
identity. The presence of mismatches was elucidated based on
the electrochemical characteristics of the redox active intercalators
bound to the DNA-modified gold surfaces. Coupled redox reactions
were employed to induce an electro-catalytic current and thus
increase the method's sensitivity (Fig. 7.4).
The effect of intervening mismatches on long-range charge
transport through DNA was comprehensively studied by Bhat-
tacharya
et al.
[35]. It was established that DNA mediates charge
transportandtheresultingoxidativedamageareextremelysensitive
to the presence of intervening mismatches. A series of DNA
oligonucleotides that incorporate a ruthenium intercalator linked
covalently to the 5' terminus of one strand and containing two
Figure 7.4.
(a) Schematic representation of electrocatalytic reduction of
[Fe(CN)
6
]
3
−
by methylene blue (MB) at a DNA-modified electrode. LB
+
is leucomethylene blue, the product of the electrochemical reduction.
(b) Cyclic voltammetry at a gold electrode modified with DNA of 2 mM
[Fe(CN)
6
]
3
−
(curve 1), 2
μ
MMB(curve2),and2mM[Fe(CN)
6
]
3
−
and 2
μ
M
MB (curve 3). Reproduced from S. O. Kelly, E. M. Boon, J. K. Barton, N. M.
Jackson, and M. G. Hill, Single-base mismatch detection based on charge
transduction through DNA,
Nucleic Acids Research
, 1999,
27
(24), 4830-
4837, by permission of Oxford University Press.
