Biology Reference
In-Depth Information
at negative potentials [47-49]. The difference in electrochemical
behavior between DNA and RNA mini-hairpins may be explained by
the conformational difference (DNA B form and RNA A form) in the
stem structures [50].
11.5 EVLS of Nucleobases and Oligonucleotides in the
Presence of Copper Ions
The purine ring is reducible on mercury electrodes in slightly
acidic medium in a wide pH scale. The electrode redox mechanism
is known and was reviewed [51, 52]. Electrochemical analysis
based on adsorptive properties of long ODNs containing purine
nucleobases, where the transfer technique involves an electrode
transfer step, cannot be applied to monomeric units of nucleotides
or nucleobases because these substances have much less absorba-
bility on electrode surfaces compared to long ODNs. New analyt-
ical approaches were developed to overcome this disadvantage.
One possibility is the interaction of purine nucleobases or their
derivatives with metal ions for example, Cu(II) ions resulting
under suitable conditions in the formation of the complex Cu(I)-
purine. In this reaction, the required monovalent copper ions are
generated electrochemically in the vicinity of electrode surface. The
formed complex is adsorbed on an electrode surface and in the
following reaction step is stripped from the surface by changing
the potential either cathodically (mercury electrodes) or anodically
(carbon electrodes). In both cases, the stripping process resulted in
the formation of a new peak on the voltammetric curve and in the
enhancement of the corresponding redox signal. Using EVLS to the
Cu(I)-purine complex analysis, the more sensitive determination of
purine derivatives was achieved.
11.5.1
Mercury and Mercury-Modified Electrodes
Under specific conditions, adenine forms an intermediate Cu(I)-
adenine species which is sparingly soluble and adsorbs strongly on
the mercury surface [53-55]. The reaction involves electrochemical
reduction of Cu(II) to Cu(I) at a suitable potential and the reaction
