Biology Reference
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of the metal complex indicator that binds to DNA (such
as [Co(phen)
3
]
3
+
[14, 44-46]) or into enhancement of the
voltammetricresponseofthenegativelychargedmetalcomplex
like [Fe(CN)
6
]
3
-
/
4
-
, which is repulsed by the negatively charged
DNA layer depending on the degree of DNA damage [47, 48].
Change in the indicator electrochemical response depends on
the portion of DNA damaged in the cleavage reaction. Similarly,
a decrease in the charge transfer resistance at an impedimetric
biosensor with hexacyanoferrate as the redox indicator in
solution was used [47, 48].
These types of DNA detection can also be applied to studies of
antioxidative properties of various natural substances preserv-
ing DNA from damage [49, 50]. The detection scheme exploits
quantification of the DNA portion that survives previous incu-
bation of the biosensor in a mixture of the DNA cleavage agent
and antioxidant/mixture of antioxidants under investigation.
Using this approach, yeast polysaccharides, phenolic acids such
as rosmarinic and caffeic acids, selected flavonoids, as well as
aqueous plant extracts and tea extracts were studied [51].
(c) Guanine residues' redox responses [13, 14]. Among DNA base
residues, those of guanine not only possess electrochemical
response but are also the most frequent target for a range
of genotoxic agents. Consequently, the guanine residues' redox
responses represent the most frequently used approach for
DNA damage detection. Decrease in the guanine peak current
relative to that yielded by undamaged DNA represents the
response to damage to the nucleobase and/or its release from
the polynucleotide chains, which is an event often following
modifications within the guanine imidazole ring. Since natural
DNA contains many guanine residues, partial decrease in the
guanine peaks is usually observed, depending on the extent of
DNA damage.
In contrast to analysis with HMDE, MFE, or AgSAE, measure-
ments of the guanine oxidation signal at carbon electrodes
(GCE,CPE,SPCE)cannotprovideinformationaboutformationof
individual sb due to a lack of differences in the signal intensity
of sc and dsDNA (both oc and lin DNA that possess free ends)
butcanbeusedformonitoringdeepDNAdegradation,involving
