title: Relaxation Process of Photoexcited meso-Naphthylporphyrins while Interacting with DNA and Singlet Oxygen Generation.
abstract: Electron donor-connecting cationic porphyrins meso-(1-naphthyl)-tris(N-methyl-p-pyridinio)porphyrin (1-NapTMPyP) and meso-(2-naphthyl)-tris(N-methyl-p-pyridinio)porphyrin (2-NapTMPyP) were designed and synthesized. DFT calculations speculate that the photoexcited states of 1- and 2-NapTMPyPs can be deactivated via intramolecular electron transfer from the naphthyl moiety to the porphyrin moiety. However, the quenching effect through the intramolecular electron transfer is insufficient, possibly due to the orthogonal position of the electron donor and the porphyrin ring and the relatively small driving force: Gibbs energies are 0.11 and 0.07 eV for 1- and 2-NapTMPyPs, respectively. It was speculated that more than 0.3 eV of the driving force is required to realize effective electron transfer in similar electron-donor connecting porphyrin systems. These porphyrins aggregated around the DNA strand, accelerating the deactivation of their excited singlet state and decreasing their photosensitized singlet oxygen-generating activities. In the presence of a sufficiently large concentration of DNA, these porphyrins can bind to a DNA strand stably, leading to an increased fluorescence quantum yield and lifetime. Singlet oxygen generation was also suppressed by the aggregation of porphyrins around DNA. Although the quantum yield of singlet oxygen generation was recovered in the presence of sufficient DNA, the singlet oxygen generated by DNA-binding porphyrins was significantly smaller than that without DNA. These results suggest that DNA-binding drugs limit the generation of photosensitized singlet oxygen by quenching the DNA strand.
authors.affiliation: Applied Chemistry and Biochemical Engineering Course, Department of Engineering, Graduate School of Integrated Science and Technology, Shizuoka University , Johoku 3-5-1, Naka-ku, Hamamatsu, Shizuoka 432-8561, Japan.|Department of Optoelectronics and Nanostructure Science, Graduate School of Science and Technology, Shizuoka University , Johoku 3-5-1, Naka-ku, Hamamatsu, Shizuoka 432-8561, Japan.
authors.forename: Kazutaka
authors.initials: K
authors.lastname: Hirakawa
authors.affiliation: Applied Chemistry and Biochemical Engineering Course, Department of Engineering, Graduate School of Integrated Science and Technology, Shizuoka University , Johoku 3-5-1, Naka-ku, Hamamatsu, Shizuoka 432-8561, Japan.
authors.forename: Makoto
authors.initials: M
authors.lastname: Taguchi
authors.affiliation: Medical Photonics Research Center, Hamamatsu University School of Medicine , Handayama 1-20-1, Higashi-ku, Hamamatsu, Shizuoka 431-3192, Japan.
authors.forename: Shigetoshi
authors.initials: S
authors.lastname: Okazaki
mesh_terms: D004247:DNA / Q000737:chemistry*; D055668:Photochemical Processes; D011166:Porphyrins / Q000737:chemistry*; D026082:Singlet Oxygen / Q000737:chemistry*
chemical_list: D011166:Porphyrins; D026082:Singlet Oxygen; D004247:DNA