@misc{oai:repo.qst.go.jp:00068829,
 author = {Nakanishi, Ikuo and Ohkubo, Kei and Kawashima, Tomonori and Kawaguchi, Kumiko and Nyuui, Minako and Takusagawa, Mitsuko and Manda, Sushma and Suenobu, Tomoyoshi and Fukuhara, Kiyoshi and Okuda, Haruhiro and Kanazawa, Hideko and Miyata, Naoki and Ozawa, Toshihiko and Anzai, Kazunori and Fukuzumi, Shunichi and Ikota, Nobuo and 中西 郁夫 and 川島 知憲 and 乳井 美奈子 and 田草川 光子 and Ｍａｎｄａ Ｓｕｓｈｍａ and 小澤 俊彦 and 安西 和紀 and 伊古田 暢夫},
 month = {Nov},
 note = {Fullerenes, such as C60 and C70, have attracted considerable interest as a potent candidate for photodynamic therapy agents, since they are sensitive to light at wavelengths longer than 500 nm.  We have recently reported that water-soluble gamma-cyclodextrin-bicapped C60 (C60/gamma-CyD) shows an efficient DNA cleaving-activity in the presence of NADH in phosphate buffer (pH 7.4) under visible-light irradiation.  C60-/gamma-CyD, generated via photoinduced electron transfer from NADH to the triplet excited state 3C60*/gamma-CyD, reduces O2 to produce superoxide anion (O2-).  We herein report the photoreactivity of C70/gamma-CyD in comparison with that of C60/gamma-CyD in aqueous systems.
An efficient DNA cleavage was observed after visible-light irradiation of the C70/gamma-CyD-NADH-O2 system in phosphate buffer (10 mM, pH 7.4).  SOD shows no inhibitory effect on the DNA cleavage, while addition of catalase significantly inhibits the DNA cleavage.  These results demonstrate that the mechanism of the DNA photocleavage by C70/gamma-CyD is essentially the same as that by C60/gamma-CyD.  In fact, the triplet-triplet absorption band at 960 nm due to 3C70*/gamma-CyD was observed after nanosecond laser pulse excitation by the laser flash photolysis of an aqueous solution of C70/gamma-CyD and NADH.  The electron transfer rate from NADH to 3C70*/gamma-CyD (ket = 6.8 x 10^7 M-1 s-1) is slightly slower than that to 3C60*/gamma-CyD (ket = 1.0 x 10^8 M-1 s-1).  However, no formation of C70-/gamma-CyD was detected by the laser flash photolysis measurements in contrast with the case of C60/gamma-CyD.  This indicates that HC70-/gamma-CyD is produced via photoinduced two-electron reduction of C70/gamma-CyD by NADH because of the higher basicity of C70-, reducing O2 via deprotonation to produce O2-., 13th Annual Meeting of the Society for Free Radical Biology and Medicine (SFRBM)},
 title = {DNA Cleaving-Activity of Water-Soluble C70 under Visible-Light Irradiation},
 year = {2006}
}