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Tunneling in the Hydrogen-Transfer Reaction from a Vitamin E Analog to an Inclusion Complex of 2,2-Diphenyl-1-picrylhydrazyl Radical with beta-Cyclodextrin in an Aqueous Buffer Solution at Ambient Temperature
- Title
- Tunneling in the Hydrogen-Transfer Reaction from a Vitamin E Analog to an Inclusion Complex of 2,2-Diphenyl-1-picrylhydrazyl Radical with beta-Cyclodextrin in an Aqueous Buffer Solution at Ambient Temperature
- Authors
- Nakanishi, Ikuo; Shoji, Yoshimi; Ohkubo, Kei; Fukuzumi, Shunichi
- Ewha Authors
- Shunichi Fukuzumi
- SCOPUS Author ID
- Shunichi Fukuzumi
- Issue Date
- 2021
- Journal Title
- ANTIOXIDANTS
- ISSN
- 2076-3921
- Citation
- ANTIOXIDANTS vol. 10, no. 12
- Keywords
- antioxidant; hydrogen transfer; kinetic isotope effect; tunneling
- Publisher
- MDPI
- Indexed
- SCIE; SCOPUS
- Document Type
- Article
- Abstract
- Recently, increasing attention has been paid to quantum mechanical behavior in biology. In this study, we investigated the involvement of quantum mechanical tunneling in the hydrogen-transfer reaction from Trolox, a water-soluble analog of vitamin E (alpha-tocopherol), to 2,2-diphenyl-1-picrylhydrazyl radical (DPPH center dot) in a phosphate buffer solution (0.05 M, pH 7.0). DPPH center dot was used as a reactivity model of reactive oxygen species and solubilized in water using beta-cyclodextrin (beta-CD). The second-order rate constants, k(H) and k(D), in 0.05 M phosphate buffer solutions prepared with H2O (pH 7.0) and D2O (pD 7.0), respectively, were determined for the reaction between Trolox and DPPH center dot, using a stopped-flow technique at various temperatures (283-303 K). Large kinetic isotope effects (KIE, k(H)/k(D)) were observed for the hydrogen-transfer reaction from Trolox to the beta-CD-solubilized DPPH center dot in the whole temperature range. The isotopic ratio of the Arrhenius prefactor (A(H)/A(D) = 0.003), as well as the isotopic difference in the activation energies (19 kJ mol(-1)), indicated that quantum mechanical tunneling plays a role in the reaction.
- DOI
- 10.3390/antiox10121966
- Appears in Collections:
- 자연과학대학 > 화학·나노과학전공 > Journal papers
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