Dynamic nuclear polarization at 9T using a novel 250 GHz gyrotron microwave source
Dynamic nuclear polarization at 9T using a novel 250 GHz gyrotron microwave source
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DOI：
10.1016/s1090-7807(02)00192-1
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发表时间：
2003-02-01
影响因子：
2.2
通讯作者：
Griffin, RG
中科院分区：
文献类型：
--
作者：
Bajaj, VS;Farrar, CT;Griffin, RG
在这篇通讯中，我们报道了在9T的磁场强度(g=2电子为250 GHz，(1)H为380 MHz)下，静态和旋转固体中的动态核极化(DNP)对核自旋极化的增强作用。在这些实验中，(1)在20 K温度下，I-(13)C-甘氨酸在60：40甘油/水基质中观察到高达170+/-50的氢增强；此外，我们还观察到无定向PF1-噬菌体的(15)N谱显著增强。最后，在魔角旋转(MAS)过程中，氨基酸U-(13)C，(15)N-Proline的二维(13)C-(13)C化学位移相关谱得到了类似于17的增强，证明了DNP实验对于持续捕获和计入偶极重新耦合的定量实验的稳定性。在所有情况下，我们都利用了以氮氧自由基4-氨基-TEMPO为顺磁掺杂剂的热混合DNP机理。这是迄今为止进行的频率最高的DNP实验，表明即使在较高的磁场下，使用热混合机制也可以实现显著的信号增强。这在很大程度上是由于这些实验中使用的250 GHz回旋管振荡器的高微波功率输出。(C)2003年埃尔塞维尔科学公司(美国)。版权所有。
In this communication, we report enhancements of nuclear spin polarization by dynamic nuclear polarization (DNP) in static and spinning solids at a magnetic field strength of 9 T (250 GHz for g = 2 electrons, 380 MHz for (1)H). In these experiments, (1)H enhancements of up to 170 +/- 50 have been observed in I-(13)C-glycine dispersed in a 60:40 glycerol/water matrix at temperatures of 20 K; in addition, we have observed significant enhancements in (15)N spectra of unoriented pf1-bacteriophage. Finally, enhancements of similar to17 have been obtained in two-dimensional (13)C-(13)C chemical shift correlation spectra of the amino acid U-(13)C, (15)N-proline during magic angle spinning (MAS), demonstrating the stability of the DNP experiment for sustained acquisition and for quantitative experiments incorporating dipolar recoupling. In all cases, we have exploited the thermal mixing DNP mechanism with the nitroxide radical 4-amino-TEMPO as the paramagnetic dopant. These are the highest frequency DNP experiments performed to date and indicate that significant signal enhancements can be realized using the thermal mixing mechanism even at elevated magnetic fields. In large measure, this is due to the high microwave power output of the 250 GHz gyrotron oscillator used in these experiments. (C) 2003 Elsevier Science (USA). All rights reserved.