Guanine electrode

A. Abbaspour and M.A. Mehrgardi, Electrocatalytic oxidation of guanine and DNA on a carbon paste electrode modified by cobalt hexacyanoferrate films. Anal. Chem. 76, 5690-5696 (2004). 

Shen et al. [301] have used quartz crystal microbalance to study electrochemical behavior of guanine, guansine, and guansine phosphate at gold electrodes. 

Ex situ measurements in the presence of dissolved oxygen have proved that the mixed monolayer was stable in the solution free of 6TG and guanine. Madueno etal. [Ill] have also studied adsorption and phase formation of 6TG on mercury electrode. At high potentials, the molecules were chemisorbed and were able to form a self-assembled monolayer. When the potential was scanned to more negative values, reductive desorption of the monolayer was observed. Cathodic voltam-metric peaks, which are typical of a 2D condensed phase transition, divided the potential window into two regions one, in which self-assembled monolayer was stable, and the second, in which a physisorbed state existed. 

Farias etal. [197] have presented cathodic adsorptive stripping voltammetry of guanine in the presence of copper at static mercury electrode. Cyclic voltammetry was also employed to characterize the interfacial and redox mechanisms. 

For the alkoxy receptor 12, which can also form 1 1 complexes with guanine nucleotides, the influence of the cationic site/receptor ratio on the EMF selectivity was determined (Table 2). Electrodes based on 12 and 210 mol% 9 gave similar, Nemstian responses to both 5 -GMP and 5 -AMP, as expected for an excess of cationic sites. Due to the high concentration of cation 9, the concentration of uncomplexed nucleotides in these membrane is high and a selectivity typical for a... 

The electrochemical approach discussed here relies on a number of special properties of indium tin-oxide (ITO) electrodes, which had been used in particular for spectroelectrochemistry since ITO is optically transparent and can be fabricated on glass [28, 29]. The first important attribute of ITO is the ability to access potentials up to about 1.4 V (all potentials versus SSCE) in neutral solution [29]. Second, ITO electrodes do not adsorb DNA appreciably [30], which could be anticipated from the ability of metal oxides to adsorb cationic proteins [31] polyanionic nucleic acids were therefore not expected to adsorb. This property makes ITO quite different from carbon, which allows access to relatively high potentials but strongly adsorbs DNA [32]. Third, the direct oxidation of guanine at ITO is extremely slow, even... 

The oxidation of guanine (G) and adenine (A) follows a two-step mechanism involving the total loss of four electrons and four protons showing current peaks at approximately 0.9 and 1.2 V, respectively. However, the redox properties are dependent on the pH, the ionic strength of the electrolyte, and the electrode material.2 The reader is referred to a recent review by Palecek and coworkers for a more comprehensive discussion regarding the electrochemical mechanism of the oxidation and reduction of DNA bases on carbon and mercury electrodes.3 4 Guanine oxidation is irreversible and occurs in two consecutive steps (Fig 10.1).5... 

The electrochemical behaviour and the adsorption of nucleic acid molecules and DNA constituents have been extensively studied over recent decades [1-6]. Electrochemical studies demonstrated that all DNA bases can be electrochemically oxidized on carbon electrodes [7-13], following a pH-dependent mechanism. The purines, guanine (G) and adenine (A), are oxidized at much lower positive potentials than the pyrimidines, cytosine (C) and thymine (T), the oxidation of which occurs only at very high positive potentials near the potential corresponding to oxygen evolution, and consequently are more difficult to detect. Also, for the same concentrations, the oxidation currents observed for pyrimidine bases are much smaller than those observed for the purine bases. Consequently, the electrochemical detection of oxidative changes occurring in DNA has been based on the detection of purine base oxidation peaks or of the major... 

Electrochemical oxidation of natural and synthetic DNA performed at pyrolytic graphite [16] and glassy carbon [3-6,17,18] electrodes showed that at pH 4.5 only the oxidation of the purine residues in polynucleotide chains is observed. Using differential pulse voltammetry, the less positive peak corresponds to the oxidation of guanine residues and the peak at more positive potentials is due to the oxidation of adenine residues. 

This result is in agreement with the fact that peroxynitrite induces DNA cleavage predominantly at the 5 -G of GG and GGG sequences [62]. Hence, the 5 terminal guanine residues will be in direct contact with the electrode surface. 

For longer incubation periods, 3 min at —0.60 V in concentrated DETA/ NO, the dAdo peak current remained unchanged, and the dGuo peak became smaller whereas the Gua oxidation current increases (Fig. 20.10). This experiment showed that for longer incubation times, more ONOO-is available to damage DNA and, as a consequence, more guanine residues are accessible to the electrode surface. 

G. Dryhurst, Adsorption of guanine and guanosine at the pyrolytic graphite electrode, Anal. Chim. Acta, 57 (1971) 137-149. 

DNA can be easily immobilized on GEC by simple wet-adsorption onto GEC surface (Fig. 21.1(A2)). A small drop of DNA probe in acetate saline solution pH 4.8 [58] is put onto the surface of a GEC electrode in upright position. The immobilization of the probe was allowed to proceed for 15 min without applying any potential under static conditions. After the inosine-modified DNA probe immobilization, the DNA target was detected by the intrinsic DNA oxidation signal coming from the guanine moieties. Briefly, the procedure consists of the following... 

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