Synthesis and charge transferability of DNA possessing a naphthalimide photosensitizer at an extrahelical position

DNA oligonucleotides possessing naphthalimide (NI) at the C5 position of deoxyuridine through an ethynyl-containing linker have been synthesized. Based on time-resolved laser flash photolysis, we showed that the photo-induced charge transfer occurs between NI at the C-5 position and the guanine base of DNA with almost same efficiency (1.8%) when compared to the terminal NI-modified DNA (2.3%). Photoelectrochemical experiments showed that DNA with NI immobilized on the gold electrode generated the photocurrent (28 ± 2 nA/cm2). These results revealed that the NI chromophore located in the extrahelical position could work as a good photosensitizer to induce the charge transfer in DNA.