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Direct dynamic nuclear polarization of 15N and 13C spins at 14.1 T using a trityl radical and magic angle spinning.
Solid State Nuclear Magnetic Resonance ( IF 3.2 ) Pub Date : 2019-04-02 , DOI: 10.1016/j.ssnmr.2019.03.009
Xiaoling Wang 1 , Bethany G Caulkins 2 , Gwladys Riviere 3 , Leonard J Mueller 2 , Frederic Mentink-Vigier 1 , Joanna R Long 3
Affiliation  

We investigate solid-state dynamic nuclear polarization of 13C and 15N nuclei using monoradical trityl OX063 as a polarizing agent in a magnetic field of 14.1 T with magic angle spinning at ∼100 K. We monitored the field dependence of direct 13C and 15N polarization for frozen [13C, 15N] urea and achieved maximum absolute enhancement factors of 240 and 470, respectively. The field profiles are consistent with polarization of 15N spins via either the solid effect or the cross effect, and polarization of 13C spins via a combination of cross effect and solid effect. For microcrystalline, 15N-enriched tryptophan synthase sample containing trityl radical, a 1500-fold increase in 15N signal was observed under microwave irradiation. These results show the promise of trityl radicals and their derivatives for direct polarization of low gamma, spin-½ nuclei at high magnetic fields and suggest a novel approach for selectively polarizing specific moieties or for polarizing systems which have low levels of protonation.



中文翻译:

15N和13C的直接动态核极化通过三苯甲基自由基和魔角旋转在14.1 T旋转。

我们使用14.3 T的单自由基三苯甲基OX063作为极化剂,在约100 K的魔角旋转下,研究了13 C和15 N核的固态动态核极化。我们监测了直接13 C和15的场依赖性冷冻的[ 13 C,15 N]尿素的N极化分别达到240和470的最大绝对增强因子。场分布与通过固体效应或交叉效应产生的15 N自旋极化和通过交叉效应和固体效应结合产生的13 C自旋极化一致。对于微晶,15含有三苯甲基的富含N的色氨酸合酶样品,在微波辐射下观察到15 N信号增加了1500倍。这些结果表明三苯甲基自由基及其衍生物有望在高磁场下直接极化低γ自旋1/2核,并提出了一种新的方法来选择性极化特定部分或极化具有低质子化水平的系统。

更新日期:2019-04-02
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