Relaxation Process of the Photoexcited State and Singlet Oxygen Generating Activity of Water-soluble meso-Phenanthrylporphyrin in a DNA

ABSTRACT: To examine the microenvironmental effect of DNA on the photosensitized reaction, the electron-donor-connecting porphyrin, meso-(9-phenanthryl)-tris(N-methyl-p-pyridinio)porphyrin (Phen-TMPyP), was synthesized. Phen-TMPyP can bind to oligonucleotides with two binding modes, depending on the DNA concentration. The fluorescence lifetime measurement of Phen-TMPyP shows a shorter component than that of the reference porphyrin without the phenanthryl moiety. However, the observed value is much longer than those of previously reported similar types of electron-donor-connecting porphyrins, suggesting that electron-transfer quenching by the phenanthryl moiety is not sufficient. The fluorescence quantum yield of Phen-TMPyP (5 μM) decreased with an increase in DNA concentration of up to 5 μM base pair (bp), possibly due to self-quenching through an aggregation along the DNA strand, increased with an increase in DNA concentration o