Biology Reference
In-Depth Information
In contrast to intercalation, electrostatic interactions are formed
between positively charged guest molecules and the negatively
charged DNA sugar-phosphate backbone. However, depending on
the experimental conditions, these interaction modes can also be
combined [21]. For instance, the dsDNA interaction with positively
charged metal complex compounds with aromatic ligands is
predominantlyelectrostaticatlowionicstrengthandpredominantly
intercalative at high ionic strength. The character of the binding
interaction of the components of electrically charged redox couples
(e.g., metal complexes) can be estimated from a net negative or
positive formal potential shift when the first one indicates the
stabilization of the component in a higher oxidation state over that
in a lower oxidation state, i.e., the electrostatic interaction, and the
second onecan beascribed to the intercalation [21, 62].
Therearealsocompounds,particularlyfromthedrugfamily(e.g.,
mitomycin C), that form covalent bonds with DNA bases and create
adducts yielding specific electrochemical responses [13].
The voltammetric response of association interaction relates
to an electrochemically active analyte, to an electrochemically
active species competing with analyte binding, or to guanine and
8-oxoguanine. Using an impedimetric DNA biosensor, distortion
of the surface-attached DNA can also be specified by appropriate
changes in the resistance of the charge transfer and capacity of the
surface layer. Impedimetric measurements provide also the possi-
bility of detecting electrochemically inactive analytes, which do not
bring about remarkable changes in the guanine oxidation current
[18, 19]. Recently, impedimetry performed in the presence of inter-
calators has been reported to specify the type of DNA interaction
[63].
1.3.3.2 Binding of proteins
UsingDNAbiosensors,twotypesofDNA-proteininteractionscanbe
investigated: first, detection of catalytic activity of DNA-processing
enzymes such as nucleases, ligases, and polymerases; and second,
a
nity interactions of DNA with proteins that can but need not be
enzymes. The detection techniques used can be the same as those
mentioned above for DNA hybridization sensors. Electroactivity of
