Reactivity of Superoxide Radical Anion with Cyclic Nitrones: Role of Intramolecular H-Bond and Electrostatic Effects
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- 作者：Frederick A. Villamena ; Shijing Xia ; John K. Merle ; Robert Lauricella ; Beatrice Tuccio ; Christopher M. Hadad ; Jay L. Zweier
- 刊名：Journal of the American Chemical Society
- 出版年：2007
- 出版时间：July 4, 2007
- 年：2007
- 卷：129
- 期：26
- 页码：8177 - 8191
- 全文大小：284K
- 年卷期：v.129,no.26(July 4, 2007)
- ISSN：1520-5126
文摘
Limitations exist among the commonly used cyclic nitrone spin traps for biological free radicaldetection using electron paramagnetic resonance (EPR) spectroscopy. The design of new spin traps forbiological free radical detection and identification using EPR spectroscopy has been a major challengedue to the lack of systematic and rational approaches to their design. In this work, density functional theory(DFT) calculations and stopped-flow kinetics were employed to predict the reactivity of functionalized spintraps with superoxide radical anion (O2
-). Functional groups provide versatility and can potentially improvespin-trap reactivity, adduct stability, and target specificity. The effect of functional group substitution at theC-5 position of pyrroline N-oxides on spin-trap reactivity toward O2- was computationally rationalized atthe PCM/B3LYP/6-31+G(d,p)//B3LYP/6-31G(d) and PCM/mPW1K/6-31+G(d,p) levels of theory. Calculatedfree energies and rate constants for the reactivity of O2- with model nitrones were found to correlate withthe experimentally obtained rate constants using stopped-flow and EPR spectroscopic methods. New insightsinto the nucleophilic nature of O2- addition to nitrones as well as the role of intramolecular hydrogen bondingof O2- in facilitating this reaction are discussed. This study shows that using an N-monoalkylsubstitutedamide or an ester as attached groups on the nitrone can be ideal in molecular tethering for improvedspin-trapping properties and could pave the way for improved in vivo radical detection at the site ofsuperoxide formation.
-). Functional groups provide versatility and can potentially improvespin-trap reactivity, adduct stability, and target specificity. The effect of functional group substitution at theC-5 position of pyrroline N-oxides on spin-trap reactivity toward O2- was computationally rationalized atthe PCM/B3LYP/6-31+G(d,p)//B3LYP/6-31G(d) and PCM/mPW1K/6-31+G(d,p) levels of theory. Calculatedfree energies and rate constants for the reactivity of O2- with model nitrones were found to correlate withthe experimentally obtained rate constants using stopped-flow and EPR spectroscopic methods. New insightsinto the nucleophilic nature of O2- addition to nitrones as well as the role of intramolecular hydrogen bondingof O2- in facilitating this reaction are discussed. This study shows that using an N-monoalkylsubstitutedamide or an ester as attached groups on the nitrone can be ideal in molecular tethering for improvedspin-trapping properties and could pave the way for improved in vivo radical detection at the site ofsuperoxide formation.