Chemiluminescence of Cypridina Luciferin Analogs. Part 3. MCLA Chemiluminescence with Singlet Oxygen Generated by the Retro-Diels-Alder Reaction of a Naphthalene Endoperoxide |
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| Authors: | Ken Fujimori Tomoko Komiyama Hideo Tabata Takayuki Nojima Katsuya Ishiguro Yasuhiko Sa-waki Hidetaka Tatsuzawa Minoru Nakano |
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| Institution: | Department of Chemistry, University of Tsukuba, Tsukuba, Ibaraki, Japan;Department of Applied Chemistry, Graduate School of Engineering, Nagoya University, Chikusa, Nagoya, Japan;Marine Biotechnology Institute, Sodesi-cho, Shimizu, Shizuoka, Japan;Department of Photon and Free Radical Research, Japan Immunoresearch Laboratories Co. Ltd., Nishiyokote-cho, Takasaki, Japan |
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| Abstract: | The chemiluminescence of the Cypridina luciferin analog, 2-methyl-6-(p-methoxyphenyl)-3,7-dihydroirnidazo1,2-a]pyrazin-3-one (MCLA), with O2 (1Δg) generated by the retro-Diels-Alder reaction of 3-(4′-methyI-l'-naphthyl)-propionic acid endoperoxide was studied in an aqueous solution with pH 7.12 at 37°C. The retro-Diels-Alder reaction occurs with a first-order rate constant of (4.16 ± 0.13) × 10?4/s to quantitatively yield O2 (1Δg) and 3-(4′-methyl-l'-naphthyl (-propionic acid. MCLA consumed equimolar amounts of O2 (1Δg) with a second-order rate constant (6.96 ± 0.27) × 108/M/s to emit light in an aqueous solution with pH 7.12 at 37°C. The chemiluminescence spectrum was identified as the fluorescence spectrum of 2-acetylamino-5-(p-methoxyphenyl)pyrazine (OMCLA), a major chemiluminescence reaction. Chemiluminescence spectra and product yields for MCLA reactions with O21Δg, with O2 (3Σ?g) and with superoxide anion radicals are identical, suggesting that all of these reactions occur via a common MCLA-2-hydrope-roxide intermediate formed by a combination of MCLA radicals and superoxide anion radicals. We have established practical use of NEPO as an O2 (1Δg) source and MCLA as a biological probe for detecting O2 (1Δg). |
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