Biology Reference
In-Depth Information
DNA, can considerably contribute to the electrochemical analysis of
nucleic acids [7].
11.4.1
AdS EVLS of Homo- and Hetero-oligonucleotides
The EVLS has been frequently utilized in the electrochemical
research of short synthetic homo- and hetero-ODNs [10, 15, 44].
Similar to the nucleobases on HMDE, EVLS has been able to resolve
the overlapped reduction signals of adenine (A) and cytosine (C)
in mixtures of dA9 and dC9 [10]. On the other hand, while EVLS
function E4 provides for the nucleobases only enhanced signals due
to the transport of electroactive species to the electrode surface
controlled only by diffusion, in case of ODNs a typical peak-
counterpeak-shaped signal is observed, indicating the electrode
process of completely adsorbed species (Fig. 11.1). The height and
potential of LSV and EVLS signals were affected by the dA9/dC9
ratio, the time of accumulation, the stirring during the adsorption,
and pH. The best results were obtained when the adsorption of
ODNs was carried out at
−
100 mV for accumulation time of 120 s
understirring.WhileonLSVcurvestheonlyonereductionpeakofA
andCresidueswasobservedinallODNs,EVLSyieldedtwoseparate
peaks in dependence on A-C representation and pH. Subsequently,
our effort was aimed at the separation of A and C reduction signals
of hetero-ODNs containing nine nucleotides with different A-C
sequences, but with the same C/A ratio. We found that (i) EVLS can
be used for the resolution of reduction signals of A and C located on
the same ODN chain, and (ii) the EVLS signal is influenced by the A-
C sequence in ODN chain and pH [15]. The best resolution of both
A and C signals was observed for ODN with triple adenines in the
central part of the nonamer(Fig. 11.3).
TheresolutionofreductionsignalsofCandAresiduesinhetero-
ODNs (9-mers and 20-mers) adsorbed from a small volume on
a HMDE was performed by EVLS in combination with the AdTS
procedure[45].Thesuggestedconnectionrepresentsanew,original
detectionmethodforODNbiosensorsandprovidesthepossibilityto
distinguish between neighboring and non-neighboring bases in the
ODN chain.
