Spin relaxation effects in photochemically induced dynamic nuclear polarization spectroscopy of nuclei with strongly anisotropic hyperfine couplings
Spin relaxation effects in photochemically induced dynamic nuclear polarization spectroscopy of nuclei with strongly anisotropic hyperfine couplings
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DOI：
10.1021/ja0705792
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发表时间：
2007-07-25
影响因子：
15
通讯作者：
Hore, P. J.
中科院分区：
文献类型：
--
作者：
Kuprov, Ilya;Craggs, Timothy D.;Hore, P. J.
我们描述了在纳秒时间尺度上F-19标记的双酸盐自由基对演化过程中发生的核和电子自旋弛豫过程的实验结果和理论模型。在10T以上的磁场中，电子-核偶极交叉驰豫和纵向Delta HFC-Delta g(超精细耦合各向异性-g-张量各向异性)相互关联的速度可以忽略不计。最主要的驰豫过程是横向Delta HFC-Delta g互关联，在足够大的旋转关联时间内，这将导致双星F-19化学诱导动态核极化(CIDNP)相的反转。这种倒置最近被实验观察到，并被用作部分变性蛋白质的局部迁移率的探针(Khan，F.；et al.J.Am化学。SoC。2006年、128年、10729-10737)。所采用的自旋动力学模型的基本特征是使用了完全的自旋态空间和完全的弛豫超算符。根据已报道的结果，我们推荐这种方法来可靠地处理松弛效应很重要的磁动力学系统。
We describe experimental results and theoretical models for nuclear and electron spin relaxation processes occurring during the evolution of F-19-labeled geminate radical pairs on a nanosecond time scale. In magnetic fields of over 10 T, electron-nucleus dipolar cross-relaxation and longitudinal Delta HFC-Delta g (hyperfine coupling anisotropy - g-tensor anisotropy) cross-correlation are shown to be negligibly slow. The dominant relaxation process is transverse Delta HFC-Delta g cross-correlation, which is shown to lead to an inversion in the geminate F-19 chemically induced dynamic nuclear polarization (CIDNP) phase for sufficiently large rotational correlation times. This inversion has recently been observed experimentally and used as a probe of local mobility in partially denatured proteins (Khan, F.; et al. J. Am. Chem. Soc. 2006, 128, 10729-10737). The essential feature of the spin dynamics model employed here is the use of the complete spin state space and the complete relaxation superoperator. On the basis of the results reported, we recommend this approach for reliable treatment of magnetokinetic systems in which relaxation effects are important.