Fig. 1.

DNA charge transfer detection system. (a) Photobleaching of the fluorescent dyes by DNA charge transfer. The NI and fluorescent dye (Fl) are represented by blue and red, respectively. The fluorescent dye is oxidized when the charge can freely migrate through DNA, leading to the photobleaching of the dyes. In the presence of the mismatch site, the charge transfer to the dyes is inhibited. (b) The positive charge injection (hole) process via A-hopping and the following charge transfer to the reporter fluorophore. Excitation of NI by UV light generates NI in the singlet excited state, which oxidizes the adjacent A base to give the contacted ion pair. The positive charge on the A base escapes from the ion pair and migrates to the nearest G through hopping between A bases to provide the charge separated state with a long lifetime. The hole injected into DNA migrates to the fluorescent dye, leading to the irreversible reaction of the reporter fluorophore.