Helium-cooling and -spinning dynamic nuclear polarization for sensitivity-enhanced solid-state NMR at 14 T and 30 K
Helium-cooling and -spinning dynamic nuclear polarization for sensitivity-enhanced solid-state NMR at 14 T and 30 K
复制标题
DOI：
10.1016/j.jmr.2012.09.008
复制
发表时间：
2012-12-01
影响因子：
2.2
通讯作者：
Fujiwara, Toshimichi
中科院分区：
文献类型：
--
作者：
Matsuki, Yoh;Ueda, Keisuke;Fujiwara, Toshimichi
我们描述了一个H-1极化增强通过动态核极化（DNP）在很低的样品温度T接近30 K的魔角旋转（MAS）条件下的灵敏度增强的固态NMR测量。实验在14.1T的高外场强度下进行。对于T10 h的MAS DNP实验，在nu（R）约为3 kHz的MAS下，液体He消耗约为16 L/h。作为微波源，我们采用了高功率，连续频率可调谐回旋管。在T接近34 K时，观察到有和无MAS的H-1 DNP增强因子分别为47和23。在这些观察的基础上，考虑到样品温度和外场强度在DNP实验中使用的效果的总NMR灵敏度的讨论。它被确定为使用低样品温度和高的外部场通常是有益的总的灵敏度，尽管在较低的温度下的较慢的极化建立和较低的DNP效率在较高的字段。这些发现突出了当前连续波DNP技术在非常高的场条件下也适用于分析大型复杂系统（如生物大分子）的潜力。(C)2012 Elsevier Inc. All rights reserved.
We describe a H-1 polarization enhancement via dynamic nuclear polarization (DNP) at very low sample temperature T approximate to 30 K under magic-angle spinning (MAS) conditions for sensitivity-enhanced solid-state NMR measurement. Experiments were conducted at a high external field strength of 14.1 T. For MAS DNP experiments at T 10 h under MAS at nu(R) approximate to 3 kHz with liquid He consumption of approximate to 16 L/h. As a microwave source, we employed a high-power, continuously frequency-tunable gyrotron. At T approximate to 34K, H-1 DNP enhancement factors of 47 and 23 were observed with and without MAS, respectively. On the basis of these observations, a discussion on the total NMR sensitivity that takes into account the effect of sample temperature and external field strength used in DNP experiments is presented. It was determined that the use of low sample temperature and high external field is generally rewarding for the total sensitivity, in spite of the slower polarization buildup at lower temperature and lower DNP efficiency at higher field. These findings highlight the potential of the current continuous-wave DNP technique also at very high field conditions suitable to analyze large and complex systems, such as biological macromolecules. (C) 2012 Elsevier Inc. All rights reserved.