In situ temperature jump high-frequency dynamic nuclear polarization experiments: Enhanced sensitivity in liquid-state NMR spectroscopy
In situ temperature jump high-frequency dynamic nuclear polarization experiments: Enhanced sensitivity in liquid-state NMR spectroscopy
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DOI：
10.1021/ja0611947
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发表时间：
2006-07-26
影响因子：
15
通讯作者：
Griffin, Robert G.
中科院分区：
文献类型：
--
作者：
Joo, Chan-Gyu;Hu, Kan-Nian;Griffin, Robert G.
我们描述了一个实验，即原位跳温动态核极化 (TJ-DNP)，该实验被证明可以增强低伽马自旋（C-13、N-15 等）液态 NMR 实验的灵敏度。该方法包括使用高频 (140 GHz) 微波和双自由基极化剂在低温下极化样品，然后用 10.6 Am 红外辐射脉冲将其快速熔化，然后在存在的情况下观察 NMR 信号。脱钩。在没有弛豫引起的偏振损失的情况下，增强量应为 epsilon(dagger) = epsilon(T-obs/T-mu wave)，其中 epsilon(dagger) 是观测到的增强量，epsilon 是在发生偏振过程的温度下获得的增强量，T-mu 波和 T-obs 分别是偏振温度和观测温度。在单个实验周期中，当使用 140 GHz 回旋管微波源、T-mu 波 = 90 K、T-obs = 300 K 时，我们观察到 C-13 信号在 120-400 范围内的室温增强 epsilon（匕首）。此外，我们证明该实验可以循环使用以执行当代 NMR 波谱中常见的信号平均。目前该实验适用于可反复冻融的样品。 TJ-DNP 还可以作为快速采集多维光谱实验中的初始偏振步骤。
We describe an experiment, in situ temperature jump dynamic nuclear polarization (TJ-DNP), that is demonstrated to enhance sensitivity in liquid-state NMR experiments of low-gamma spins - C-13, N-15, etc. The approach consists of polarizing a sample at low temperature using high-frequency (140 GHz) microwaves and a biradical polarizing agent and then melting it rapidly with a pulse of 10.6 Am infrared radiation, followed by observation of the NMR signal in the presence of decoupling. In the absence of polarization losses due to relaxation, the enhancement should be epsilon(dagger) = epsilon(T-obs/T-mu wave), where epsilon(dagger) is the observed enhancement, epsilon is the enhancement obtained at the temperature where the polarization process occurs, and T-mu wave and T-obs are the polarization and observation temperatures, respectively. In a single experimental cycle, we observe room-temperature enhancements, epsilon(dagger), of C-13 signals in the range 120-400 when using a 140 GHz gyrotron microwave source, T-mu wave = 90 K, and T-obs = 300 K. In addition, we demonstrate that the experiment can be recycled to perform signal averaging that is customary in contemporary NMR spectroscopy. Presently, the experiment is applicable to samples that can be repeatedly frozen and thawed. TJ-DNP could also serve as the initial polarization step in experiments designed for rapid acquisition of multidimensional spectra.