2,6-Diaminopurine nucleoside derivative of 9-ethyloxy-2-oxo-1,3- diazaphenoxazine (2-amino-Adap) for recognition of 8-oxo-dG in DNA

8-Oxo-2′-deoxyguanosine (8-oxo-dG) is a nucleoside resulting from oxidative damage and is known to be mutagenic. 8-Oxo-dG has been related to aging and diseases, including neurological disorders and cancer. Recently, we reported that a fluorescent nucleoside derivative, adenosine-1,3- diazaphenoxazine (Adap), forms a stable base pair with 8-oxo-dG in DNA with accompanying efficient quenching. In this study, a new Adap derivative having an additional 2-amino group on the adenosine moiety (2-amino-Adap) was designed with the anticipation of additional hydrogen bonding with the 8-oxo group of 8-oxo-dG. The properties of the ODN containing 2-amino-Adap were evaluated by measuring thermal stability and fluorescence quenching. In contrast to the previously designed Adap, the base-pairing and fluorescence quenching properties of 2-amino-Adap varied depending on the ODN sequence, and there was no clear indication of an additional hydrogen bond with 8-oxo-dG. Instead, the base pairing of 2-amino-Adap with dG was significantly destabilized compared with that of Adap with dG, resulting in improved selectivity for 8-oxo-dG in the human telomere DNA sequence. Thus, the telomere-targeting ODN probe containing 2-amino-Adap displayed selective, sensitive and quantitative detection of 8-oxo-dG in the human telomere DNA sequence in a light-up detection system using SYBR Green.