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Figure 7.8. Electrochemical impedance measurements in the presence
of [Fe(CN) 6 ] 3 / 4 of (a) matched and (c) single mismatched ds-DNA films;
(b) and (d) schematically represent MutS interactions with matched and
mismatched films, respectively. Please note the significant increase in the
impedance signal as a function of MutS bound to the surface, causing a
significant increase in the charge transfer resistance. C.-Z. Li, Y.-T. Long, J.
S. Lee, and H.-B. Kraatz, Chem. Commun. , 2004, 574-575. Reproduced by
permission of the Royal Society of Chemistry.
different mismatches in the order of GT > CT > CC by CV and EIS on
modifiedgoldelectrodes.Han et al. [67]approachedtheproblemin
a slightly different way. Instead of tagging DNA mismatched duplex,
they tagged gold electrode through a histidine-Ni-nitriloacetate
complexandmeasuredthecurrentdecreaseduetotheelectrostatic
repulsion between the anionic redox probe and polyanionic DNA
bound to MutS on the electrode. The detection limit of about 500
fM for a G-T mismatch is certainly encouraging. Furthermore, the
signal strength varies with the nature of the mismatch according
to TG > GG > AC = AA = AG > TT > CT > CC. A more complex approach
was adopted by Chen et al. [68] involving the binding of
methylene blue labeled mismatched DNA to MutS immobilized
 
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