Biology Reference
In-Depth Information
by additional reagent N-hydroxysulfosuccinimide (NHS) in order to
activate carboxyl groups on the carbon electrode.
Single-stranded amino-linked DNA or label-free short DNA
sequences are bound to these groups by their amino tags [21] and
deoxyguanosineresidues, respectively [20].
On the other hand, covalent agents can also be applied to the
unpreated carbon surface directly before DNA immobilization onto
activated sites of carbodiimide compounds [21].
12.4.3
DNA
˙
Immobilization onto Transducer Surfaces via
Avidin-Biotin
˙
Interaction
Biotin binds very tightly to the tetrameric protein avidin (also
streptavidin and neutravidin), with a dissociation constant
K
d
in
the order of 10
−
15
, which is one of the strongest known protein-
ligand interactions, the strength being approximately due to the the
covalent bond[22].
12.5 DNA-Compound Interactions
Voltammetric methods can be used for (1) the identification of
DNA strand breakage and damage, and (2) the determination of
electroactive compounds that specifically bind to DNA (covalently
and/or noncovalently) [23]. For these purposes, electrochemical
DNA biosensors based on the investigation of DNA-compound
interactionshasbeenextensivelystudiedwithanumberofdifferent
techniques in the past 15 years and this subject has attracted
increasing attention due to its important roles in living organisms
toward the aim of inexpensive and rapid analysis in molecular
biology.
Electrochemical DNA biosensors offer sensitivity, selectivity, and
low-cost detection in this field; therefore, numerous voltammetric
approacheshavebeendevelopedcontainingdirectelectrochemistry
of DNA bases and electrochemistry of DNA-specific electroactive
mediators (reporters) [24, 25].
