Synthesis and optical behaviors of 6-seleno-deoxyguanosine

We have developed a simple method to synthesize 6-seleno-2′-deoxyguanosine (^SedG) by selectively replacing the 6-oxygen atom with selenium. This selenium-atom-specific modification (SAM) alters the optical properties of the naturally occurring 2′-deoxyguanosine (dG). Unlike the native dG, the UVabsorption of ^SedG is significantly influenced by the pH of the aqueous solution. Moreover, ^SedG is fluorescent at the physiological pH and exhibits pH-dependent fluorescence in aqueous solutions. Furthermore, ^SedG has noticeable fluorescence in non-aqueous solutions, indicating its sensitivity to environmental changes. This is the first time a fluorescent nucleoside by single-atom alteration has been observed. Fluorescent nucleosides modified by a single atom have great potential as molecular probes with minimal perturbations to investigate nucleoside interactions with proteins, such as membrane-transporter proteins.