Loading…
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...
Saved in:
Published in: | The journal of physical chemistry. B 2005-05, Vol.109 (20), p.10521-10530 |
---|---|
Main Authors: | , , , , |
Format: | Article |
Language: | English |
Subjects: | |
Citations: | Items that this one cites Items that cite this one |
Online Access: | Get full text |
Tags: |
Add Tag
No Tags, Be the first to tag this record!
|
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 |