Guanine, metal complexes

A number of lines of evidence suggested early on that 8-oxo-7,8-dihydrogua-nine (8G) is more readily oxidized than guanine [42, 86-88]. The most direct evidence in this regard was the ability to detect 8G selectively using electrochemical detectors in liquid chromatography [89]. We therefore suspected that 8G would react with metal complexes with potentials lower than... 

A number of transition metal complexes exhibit rich photoredox properties, which allow studies of photocleavage of DNA via guanine oxidation [10], photoinduced electron-transfer reactions in metalloproteins [11], and the use... 

Enhanced electrochemical signals for DNA can be obtained by catalytic electrochemical oxidation using transition metal complexes/341 Studies by Thorp et al/35 01 showed that Ru(bpy)f+ (bpy=2,2 -bipyridine) is an efficient electrochemical catalyst that oxidizes only guanine bases in DNA and oligonucleotides. The reaction follows the catalytic pathway below ... 

The ability to calculate redox potentials has powerfid implications. For example, elecfrocatalytic reactions of metal complexes, such as Ru(bpy)3 +, with DNA nucleobases, such as guanine, provide a sensitive method for detection of nucleic acids on surfaces in electrochemical DNA chips (see Nucleic Acid-Metal Ion Interactions) In these reactions, voltammetric oxidation of Ru(bpy)3 + to Ru(bpy)3 + in the presence of guanine produces an enhancement in the oxidative current due to the reaction of Ru(III) with guanine (Figure 2). On surfaces, the extent of elecfrocatalytic enhancement is indicative of the quantity of bound nucleic acid levels of DNA as low as 40 attomoles have been detected using related methods. ... 

Besides hydrophobic and coordinative interactions, hydrogen bonds and electrostatic interactions have been used to assemble luminescent metal complexes. In this context, Barigelletti and coworkers (45-47) reported on the luminescent properties of Ru(II) and Os(II) complexes containing bipyridines peripherally functionalized with nucleotide bases, cytosine, and guanine. 

No. But that s OK because that kept on pushing us towards better and better experiments. I think that the last experiment that we published in Science this year may have made clear how exquisitely sensitive the electron transfer was to base-pair stacking. In this experiment we no longer appended metal complex intercalators but we simply looked at electron transfer from one modified base to another modified base. In this experiment we used two modified adenines as our fluorescent excited electron acceptor to oxidize guanines. The modified adenines were very similar in structure, very similar in redox characteristics, very similar in energetics. But when they were incorporated into DNA, one was well-stacked in the helix and one was... 

Electrochemical biosensing of DNA sequences using direct electrochemical detection of DNA hybridization, adsorptive striping analysis, metal complex hybridization indicators, organic compound electroactive hybridization indicators and renewable DNA probes have been considered [65,67,72,73]. With metal complexes and organic compound electroactive hybridization indicators, non-specific adsorption can influence the results [68,94]. Chrono-potentiometric detection was used to monitor the hybridization onto screen-printed carbon electrodes by following the oxidation of the guanine peak, which decreases in the presence of the complementary strand [64,68,73]. 

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