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Yamashita, Shinichi; Baldacchino, G.*; Maeyama, Takuya*; Taguchi, Mitsumasa; Muroya, Yusa*; Lin, M.*; Kimura, Atsushi; Murakami, Takeshi*; Katsumura, Yosuke
Free Radical Research, 46(7), p.861 - 871, 2012/07
Times Cited Count:24 Percentile:53.5(Biochemistry & Molecular Biology)Radiation-induced reactions in aqueous solutions of a water-soluble coumarin derivative, coumarin-3-carboxyl acid (C3CA), have been investigated by pulse radiolysis with 35-MeV electron beam, final product analysis after Co -irradiations, and deterministic model simulations. It was found that C3CA reacts with the hydroxyl radical (OH) as well as the hydrated electron at nearly diffusion-controlled rate constants: 6.810 and 2.110 Ms, respectively. Reactivity of C3CA toward O was not confirmed. Production of a fluorescent molecule 7-hydroxy-coumarin-3-carboxylic acid (7OH-C3CA) was detected by a fluorescence spectrometer coupled with high performance liquid chromatography. Production yields of 7OH-C3CA were in a range from 0.025 to 0.18 (100 eV), depending on irradiation conditions. A variety of the yield with saturating gas, additive, and C3CA concentration implied that there are at least two pathways from scavenging reaction of C3CA toward OH to 7OH-C3CA: peroxidation reaction followed by elimination of perhydroxyl radical and disproportionation reaction. A reaction mechanism involving the two pathways was proposed and incorporated into the simulations, showing good explanation of experimentally measured 7OH-C3CA yields with a constant conversion factor from OH scavenging to 7OH-C3CA production, 4.7%, unless -BuOH is not added.
Fu, H. Y.*; Lin, M.; Muroya, Yusa*; Hata, Kuniki; Katsumura, Yosuke; Yokoya, Akinari; Shikazono, Naoya; Hatano, Yoshihiko
Free Radical Research, 43(9), p.887 - 897, 2009/09
Times Cited Count:24 Percentile:46.92(Biochemistry & Molecular Biology)