Exploiting Nuclear Spin Polarization to Investigate Enzyme-Mediated Free Radical Reactions via in situ NMR

利用核自旋极化通过原位 NMR 研究酶介导的自由基反应

• 批准号: 5314680
• 负责人: Professor Dr. Joachim Bargon
• 金额: --
• 依托单位国家: 德国
• 项目类别: Priority Programmes
• 财政年份: 2001
• 资助国家: 德国
• 起止时间: 2000-12-31 至 2003-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/5314680?language=en
• 关键词: Exploiting; Nuclear; Spin; Polarization; Investigate

Radicals occuring in enzyme-mediated reactions will be studied via NMR spectroscopy using the CIDNP method. A threefold strategy will be followed: 1. Initially simple model radicals for the postulated intermediates will be generated either photochemically using an UV eximer laser or by mixing appropriate components in a flow system. Photoinitiated electron transfer between a donor (triethylamine) and as acceptor a halogen-containing precursor yields the desired neutral free radicals after eliminating a halide from the halogen-containing radical anion. The radical cation expels a proton, yielding a neutral free radical likewise. The resulting radical pairs cause CIDNP, which should allow to differentiate between the two alternative reaction pathways, i.e. fragmentation followed by recombination versus addition followed by elimination. 2. Analogously, the enzyme-produced radicals NO., HO., O2-. and their follow-up species will be generated via a flow system. 3. The associated phenomena and polarization patterns of the products will be studied initially using a conventional NMR probe, but eventually via a cylindrical torus probe, which insures higher sensitivity. This same setup has been used successfully to study homogeneous hydrogenation of unsaturated substrates using only one spin isomers of H2, typically of parahydrogen. This phenomenon, termed Parahydrogen Induced Polarization (PHIP), though different in detail, has features similar to CIDNP.

将使用CIDNP方法通过NMR光谱研究酶介导反应中发生的自由基。将采取三重战略：1。最初简单的模型自由基的假定中间体将产生光化学使用UV准分子激光或通过混合适当的成分在流动系统。光引发的电子转移之间的供体（三乙胺）和作为受体的含卤素的前体产生所需的中性自由基后，消除卤化物从含卤素的自由基阴离子。自由基阳离子排出一个质子，同样产生一个中性自由基。由此产生的自由基对引起CIDNP，这应该允许区分两种替代反应途径，即片段化后重组与加成后消除。2.类似地，酶产生的自由基NO.，嘿，O2-.并且它们的后续物种将通过流动系统产生。3.相关的现象和偏振模式的产品将首先使用传统的NMR探头，但最终通过圆柱形的环面探针，这确保了更高的灵敏度进行研究。这种相同的设置已成功地用于研究不饱和底物的均匀氢化，仅使用H2的一种自旋异构体，通常是仲氢。这种现象被称为仲氢诱导极化（PHIP），虽然在细节上有所不同，但具有与CIDNP相似的特征。