Detecção eletroquímica da 7-metilguanosina em eletrodo de carbono vítreo

The alkylation of guanosine has been a subject of many recent biochemical and analytical studies since a high concentration of 7-MeGuo may be associated with DNA damage, exposure to methylation and toxic agents, oxidative stress, cancer and other factors. DNA methylation process can naturally occur as methylation of 7-methylguanosine (7-MeGuo), Fig.1, which occurs in different tRNAs [1]. Voltammetry techniques are widely employed in medical studies for clarifying different biochemical processes that occur in vivo and for developing electroanalytical methods for determination of biological species, specially due to the high sensitivity, selectivity and adaptability of these techniques [2]. This work investigated the oxidation of 7-MeGuo in different media on glassy carbon electrode (GCE) using cyclic, differential pulse and square wave voltammetry and impedance spectroscopy. 7-MeGuo is irreversibly oxidized in a pH dependent single step reaction controlled predominantly by diffusion. The oxidation involves the transfer of one electron and one proton forming a highly reactive intermediate radical, the radical 7-MeGuo●, and polymeric products that adsorb strongly on the GCE surface. In addition, an electroanalytical method for determination of 7-MeGuo in the presence of free bases, other nucleosides and dsDNA, based on differential pulse voltammetry, was also proposed. An oxidation mechanism of 7-MeGuo was suggested and a novel biosensor for DNA-methylation detection was developed.