Biology Reference
In-Depth Information
12.6 Calculations About Compound-DNA Interactions
In order to investigate the interaction mechanism of a compound
with DNA, different approaches have been presented which can
be used in practical applications such as guanine signal-based
measurement, compound signal-baseddetection.
The change in the guanine peak is generally used for the
calculations of electrochemical DNA biosensors because guanine is
more easily oxidized than other DNA bases and it can be evaluated
as one of the key criteria for the voltammetric detection of DNA-
drug interactions. The decrease in the guanine signal is estimated
withinteractionsbetweencompoundsandDNA,thecurrentratioof
guanine(
S
%)iscalculatedaccordingtotheBagni
et al.
[34]equation
whichshown below:
S
%
=
(
S
s
/
S
b
)
×
100
According to the equation,
S
s
is the signal ratio of the peak
height of guanine after the interaction with a sample compound,
and
S
b
is the magnitude of guanine signal after the interaction
with the buffer which is used for the preparation of the related
compound. The guanine oxidation signal obtained with differential
pulsevoltammetry(DPV)inabsenceofacompoundservedas100%.
After the interaction between a compound and DNA,if it is obtained
at
S
>
85% of value, the molecule is considered nontoxic, if it
is obtained that
S
% value is between 50 and 85, compound is
evaluated moderately toxic, and if the calculation of
S
% values are
obtainedas
S
<
50%, compound is accepted as toxic.
In order to find an idea about interaction mechanism of a
compound with DNA, the other important value is “partition
coe
cient” which was investigated by Millan and Mikkelsen [20]
in 1993. The partition coe
cient value is calculated for DNA
biosensors using current signals obtained from probe modified,
hybridmodified, and bare electrodes according to the equation:
Partitioncoe
cient
=
Compound
bound
/
Compound
free
=|
(
i
bound
−
i
free
)
/
i
free
|
Here
i
free
istheelectrochemicalpeakheightofacompoundobtained
at bare electrode, and
i
bound
is the oxidation peak current of a com-
