title: Sensitive electrochemical measurement of hydroxyl radical generation induced by the xanthine-xanthine oxidase system.
abstract: A sensitive electrochemical measurement system for hydroxyl radical (OH) was developed using enzyme-catalyzed signal amplification. In the presence of 2,6-xylenol as a trapping agent, glucose as a substrate, and pyrroloquinoline quinone-dependent glucose dehydrogenase (PQQ-GDH) as a catalyst, the amperometric signal of the trapping adduct 2,6-dimethylhydroquinone (DMHQ) produced by the hydroxylation of 2,6-xylenol was able to be amplified and detected sensitively. The limit of detection (signal/noise [S/N]=3) for DMHQ was 1 nM. There was no significant interference from urate and other oxidizable compounds in the reaction mixture at the applied potential of 0V versus Ag/AgCl. This method was employed to observe the OH generation induced by the xanthine-xanthine oxidase (XO) system. The reaction rates of the DMHQ production induced from the xanthine-XO system in the presence and absence of various Fe(III) complexes and proteins were compared. Those with a free coordination site on the Fe atom effectively enhanced the OH generation.
authors.affiliation: Department of Chemistry, Faculty of Science, Shinshu University, Matsumoto, Nagano 390-8621, Japan. Electronic address: tatsumi@shinshu-u.ac.jp.
authors.forename: Hirosuke
authors.initials: H
authors.lastname: Tatsumi
authors.affiliation: Department of Chemistry, Faculty of Science, Shinshu University, Matsumoto, Nagano 390-8621, Japan.
authors.forename: Yui
authors.initials: Y
authors.lastname: Tsuchiya
authors.affiliation: Department of Chemistry, Faculty of Science, Shinshu University, Matsumoto, Nagano 390-8621, Japan.
authors.forename: Koichi
authors.initials: K
authors.lastname: Sakamoto
mesh_terms: D002384:Catalysis; D055664:Electrochemical Techniques / Q000379:methods*; D004578:Electron Spin Resonance Spectroscopy; D005290:Ferric Compounds / Q000378:metabolism*; D005947:Glucose / Q000378:metabolism*; D005948:Glucose Dehydrogenases; D006801:Humans; D006873:Hydroquinones / Q000737:chemistry; D017665:Hydroxyl Radical / Q000032:analysis* / Q000378:metabolism; D010084:Oxidation-Reduction; D019820:Xanthine / Q000378:metabolism*; D014969:Xanthine Oxidase / Q000378:metabolism*; D014992:Xylenes / Q000737:chemistry
chemical_list: D005290:Ferric Compounds; D006873:Hydroquinones; D014992:Xylenes; D019820:Xanthine; D017665:Hydroxyl Radical; C004735:2,6-dimethylhydroquinone; D005948:Glucose Dehydrogenases; D014969:Xanthine Oxidase; C036531:2,6-xylenol; D005947:Glucose
keywords: Enzyme redox cycling; Fenton reaction; Haber–Weiss mechanism; Hydroxyl radical; Signal amplification; Xanthine oxidase