Villamena Frederick A, Xia Shijing, Merle John K, Lauricella Robert, Tuccio Beatrice, Hadad Christopher M, Zweier Jay L
Department of Pharmacology, Center for Biomedical EPR Spectroscopy and Imaging, The Davis Heart and Lung Research Institute, The Ohio State University, Columbus, OH 43210, USA.
J Am Chem Soc. 2007 Jul 4;129(26):8177-91. doi: 10.1021/ja0702622. Epub 2007 Jun 12.
Limitations exist among the commonly used cyclic nitrone spin traps for biological free radical detection using electron paramagnetic resonance (EPR) spectroscopy. The design of new spin traps for biological free radical detection and identification using EPR spectroscopy has been a major challenge due 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 spin traps with superoxide radical anion (O2*-). Functional groups provide versatility and can potentially improve spin-trap reactivity, adduct stability, and target specificity. The effect of functional group substitution at the C-5 position of pyrroline N-oxides on spin-trap reactivity toward O2*- was computationally rationalized at the PCM/B3LYP/6-31+G(d,p)//B3LYP/6-31G(d) and PCM/mPW1K/6-31+G(d,p) levels of theory. Calculated free energies and rate constants for the reactivity of O2*- with model nitrones were found to correlate with the experimentally obtained rate constants using stopped-flow and EPR spectroscopic methods. New insights into the nucleophilic nature of O2*- addition to nitrones as well as the role of intramolecular hydrogen bonding of O2*- in facilitating this reaction are discussed. This study shows that using an N-monoalkylsubstituted amide or an ester as attached groups on the nitrone can be ideal in molecular tethering for improved spin-trapping properties and could pave the way for improved in vivo radical detection at the site of superoxide formation.
在使用电子顺磁共振（EPR）光谱法进行生物自由基检测时，常用的环状硝酮自旋捕集剂存在局限性。由于缺乏系统且合理的设计方法，利用EPR光谱法设计用于生物自由基检测和鉴定的新型自旋捕集剂一直是一项重大挑战。在这项工作中，采用密度泛函理论（DFT）计算和停流动力学来预测功能化自旋捕集剂与超氧阴离子自由基（O2*-）的反应活性。官能团提供了多功能性，并有可能提高自旋捕集剂的反应活性、加合物稳定性和目标特异性。在PCM/B3LYP/6-31+G(d,p)//B3LYP/6-31G(d)和PCM/mPW1K/6-31+G(d,p)理论水平上，从计算角度合理化了吡咯啉N-氧化物C-5位上官能团取代对自旋捕集剂与O2*-反应活性的影响。发现使用停流和EPR光谱法计算得到的O2*-与模型硝酮反应的自由能和速率常数与实验获得的速率常数相关。讨论了关于O2*-加成到硝酮上的亲核性质以及O2*-分子内氢键在促进该反应中的作用的新见解。这项研究表明，在硝酮上使用N-单烷基取代的酰胺或酯作为连接基团在分子连接中对于改善自旋捕集性能可能是理想的，并且可以为在超氧形成部位改进体内自由基检测铺平道路。
