Guanine N7 position

Inner-shell binding of selected hydrated metal ions (Mg, Cu, Zn, and Cd ) to the guanine N7 position was investigated in relation to outer- and inner-shell binding to an anionic phosphate group (Rulfsek and Sponer 2003). The study was focused on the mutual... 

Since the results of our experiments with isolated rat liver fractions supported a reaction sequence Initiated by microsomal oxidation of the nitrosamine leading to formation of a carbonium ion, the results of the animal experiment suggested that in the intact hepatocyte, one of the earlier electrophilic intermediates (II, III or V, Figure 1) is intercepted by nucleophilic sites in DNA (exemplified here by the N7 position of guanine) before a carbocation is formed. 

Procarbazine (Matulane) may autooxidize spontaneously, and during this reaction hydrogen peroxide and hydroxyl free radicals are generated. These highly reactive products may degrade DNA and serve as one mechanism of procarbazine-induced cytotoxicity. Cell toxicity also may be the result of a transmethylation reaction that can occur between the A-methyl group of procarbazine and the N7 position of guanine. 

When adjacent guanines are present in an oligonucleotide, cisplatin chelates to these at the N7 positions. 

The major site of alkylation within DNA is the N7 position of guanine (Figure 55-4) however, other bases are also alkylated to lesser degrees, including N1 and N3 of adenine, N3 of cytosine,... 

Another effect on DNA can result when alkylated bases are lost from the DNA polymer. For example, guanine alkylated in the N7 position has a much weakened bond to DNA and may split off from the DNA molecule ... 

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