Guanine oxidation residues

Damage to DNA by ROS may affect the thymine (43) residnes, as mentioned in Section IV.B.2 however, also guanine (160) residues of DNA are labile and may yield 8-oxoguanine (96). This fact is the basis of a qualitative in vitro immunoassay for DNA oxidative damage shown in Table 2 . ... 

Besides the direct oxidation products of base residues of DNA, such as the oxidation of thymine (43) and guanine (160) residues meutioued in Sections IV.B.2 and IV.B.3, ROS and other factors may bring about detachmeut of base residues from the DNA strand, leading to formation of aldehyde abasic sites on the main chain, as shown in... 

SsDNA/tRNA Oxidation of guanine/ adenine residues at MWCNT-modified SPCEs Cyclic voltammetry +610mV (guanine) +920mV (adenine)... 

The isolation, mass and NMR characterization of the lesions was performed with the dinucleotide model compound d(GpT) since the chromatographic separation of the products of guanine oxidation was followed easily by UV-VIS spectrophotometry (thymine base was not modified by the oxidation) and the very polar oxidized guanine residues could be retained on the reverse phase HPLC column by the dinucleotide structure of the substrate. The oxidation of the guanine moiety of a dinucleoside monophosphate under appropriate conditions afforded the imidazolone (Iz) and the dehydro-guanidinohydantoin derivative 35 in amounts compatible with NMR analysis (261). However, 35 is not stable and was first stabilized in two ways for the... 

Vialas C, Claparols C, Pratviel G () Meunier B (200) Guanine oxidation in double-stranded DNAby Mn-TMPyP/KHS05 5,8-dihydroxy-7,8-dihydroguanine residue as a key precursor of imidazolone and parabanic acid derivatives. J Am Chem Soc 122 2157-2167... 

There are examples in which base radicals undergo reaction with adjacent base residues. The 5-(2 -deoxyuridinyl)methyl radical (63, Scheme 8.30) can forge an intrastrand cross-link with adjacent purine residues. Cross-link formation is favored with a guanine residue on the 5 -side of the pyrimidine radical and occurs under low-oxygen conditions. A mechanism was not proposed for this process, but presumably the reaction involves addition of the nucleobase alkyl radical to the C8-position of the adjacent purine residue. Molecular oxygen likely inhibits crosslink formation by trapping the radical 63, as shown in Scheme 8.24. The radical intermediate 89 must undergo oxidation to yield the final cross-linked product 90,... 

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. 

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