Liquid-state Overhauser DNP at High Magnetic Fields
Liquid-state Overhauser DNP at High Magnetic Fields
复制标题
DOI：
10.1002/9780470034590.emrstm1557
复制
发表时间：
2019-01-01
期刊：
影响因子：
--
通讯作者：
Prisner, Thomas F.
中科院分区：
文献类型：
--
作者：
Denysenkov, Vasyl P.;Prisner, Thomas F.
在过去的几年里，高磁场下的动态核极化已成为磁共振波谱和成像领域最热门的技术和方法研究领域之一。许多工作致力于在固态下进行从电子自旋到核自旋的极化转移的实验，而由奥弗豪瑟效应驱动的液态极化转移的例子很少。这篇综述文章将讨论在高磁场下进行此类实验的技术要求，特别强调双共振结构，该结构允许在微波吸收溶液中进行此类实验。描述了使用硝基氧自由基单独评估决定几种有机溶剂的质子奥豪瑟动态核极化 (DNP) 增强的因素的实验程序，并与理论预测进行了比较。我们表明，在高磁场下，基于斯托克斯-爱因斯坦运动的模型低估了耦合因子，因此低估了 DNP 效率。经典模型的这种失败对于使用脂质双层样品获得的 DNP 结果最为明显。
Over the past few years, dynamic nuclear polarization at high magnetic fields has become one of the most popular technical and methodical research areas in the field of magnetic resonance spectroscopy and imaging. Much work has been devoted to experiments with the polarization transfer from the electron spin to the nuclear spin performed in the solid state, whereas only few examples exist for polarization transfer in the liquid-state, which is driven by the Overhauser effect. The technical requirements to perform such experiments at high magnetic fields will be discussed in this review article, with special emphasis on double-resonance structures, which allow performing such experiments in microwave-absorbing solutions. Experimental procedures to individually evaluate the factors determining the proton Overhauser dynamic nuclear polarization (DNP) enhancements of several organic solvents using nitroxide radicals are described and compared to theoretical predictions. We show that at high magnetic fields the models based on Stokes-Einstein motion underestimate the coupling factor and therefore the DNP efficiency. This failure of the classical model is most obvious for DNP results obtained with lipid bilayer samples.