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Inclusion Complexes of PBN-Type Nitrone Spin Traps and Their Superoxide Spin Adducts with Cyclodextrin Derivatives:  Parallel Determination of the Association Constants by NMR Titrations and 2D-EPR Simulations

1H NMR and electron paramagnetic resonance (EPR) titrations were used to determine the association constants of the complexes of α-phenyl-N-tert-butylnitrone (PBN) analogues and their superoxide spin adducts, respectively, with methylated β-cyclodextrins. A 1:1 stoichiometry for the nitrones with ra...

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Bibliographic Details
Published in:The journal of physical chemistry. B 2005-05, Vol.109 (20), p.10521-10530
Main Authors: Bardelang, David, Rockenbauer, Antal, Karoui, Hakim, Finet, Jean-Pierre, Tordo, Paul
Format: Article
Language:English
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Summary:1H NMR and electron paramagnetic resonance (EPR) titrations were used to determine the association constants of the complexes of α-phenyl-N-tert-butylnitrone (PBN) analogues and their superoxide spin adducts, respectively, with methylated β-cyclodextrins. A 1:1 stoichiometry for the nitrones with randomly methylated β-cyclodextrin and 2,6-di-O-methyl-β-cyclodextrin and 1:1 and 1:2 stoichiometries for the corresponding cyclodextrin−nitroxide complexes were observed. After the superoxide radical spin trapping reaction, EPR titrations afforded the association constants of the corresponding cyclodextrin−nitroxide complexes. Two-dimensional EPR simulations indicated a bimodal inclusion of the nitroxide free radical spin adducts into the cyclodextrins. For all the nitrone−cyclodextrin and nitroxide−cyclodextrin complexes, the association constants were always higher for the nitroxide complexes than for the nitrone complexes. A cooperative system concerning the complexation of the nitroxide spin adduct with a cyclodextrin was evidenced by EPR titrations. The efficiency of the cyclodextrin inclusion technique to trap superoxide and to resist bioreduction by sodium l-ascorbate was also investigated.
ISSN:1520-6106
1520-5207
DOI:10.1021/jp0509414