Photoinduced electron injection into DNA by N-cyclopropyl-1-aminonaphthalene

DNA containing either N-cyclopropyl-1-aminonaphthalene (cAN) or N-methyl-1-aminonaphthalene (mAN) as a photoinduced electron donor have been developed to investigate the electron injection and charge recombination processes in DNA duplex. Oxidation potentials of the photo-excited aminonaphthalenes (ANs) were estimated to be approximately −3.0 V vs. SCE, which are high enough to induce one-electron reduction of DNA bases. Photoinduced excess electron transfer in the AN-tethered DNA duplexes has been examined using gel electrophoresis, but the apparent electron-transfer efficiencies were almost the same for both of the cAN- and the mAN-tethered DNA. The marginal effect of cyclopropyl substitution on the efficiency of charge separation suggests that charge recombination in the contact radical ion pair is faster and more efficient than cyclopropane-ring opening.