Hyperpolarized Hadamard Spectroscopy Using Flow NMR
Hyperpolarized Hadamard Spectroscopy Using Flow NMR
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DOI：
10.1021/ac401293n
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发表时间：
2013-08-06
影响因子：
7.4
通讯作者：
Hilty, Christian
中科院分区：
文献类型：
--
作者：
Chen, Hsueh-Ying;Hilty, Christian
溶解动态核极化(D-DNP)技术的出现为克服核磁共振实验固有的灵敏度限制提供了重要的突破。在溶解DNP中，只有少量的冷冻样品被极化、溶解并注入核磁共振光谱仪。虽然可以获得显著增强的核磁共振信号，但这种技术的单次扫描特性先验地阻碍了相关实验的使用，而相关实验代表了核磁共振光谱的一些最强大的应用。在这里，描述了一种利用流动核磁共振探针从D-DNP样品中进行多扫描光谱分析的替代方法。使用专门设计的装置顺序注入多个超极化样品段。阿达玛光谱可以应用于获得化学位移相关信息，即使从少量的扫描。这一能力通过四次扫描数据集得到测试分子1-丁醇中的[C-13，H-1]相关性得到了证明。由于D-DNP实验中自旋晶格驰豫和浓度梯度的影响，Hadamard重建的减法过程需要一个额外的强度标度步骤。为此，开发了一种重建过程，该过程使用了熵最大化，并且对于噪声和信号重叠是稳健的。在更广泛的意义上，这里描述的多扫描核磁共振适用于各种相关核磁共振实验，并增加了D-DNP在小分子表征中的多功能性。
The emergence of the dissolution dynamic nuclear polarization (D-DNP) technique provides an important breakthrough to overcome inherent sensitivity limitations in nuclear magnetic resonance (NMR) experiments. In dissolution DNP, only a small amount of frozen sample is polarized, dissolved, and injected into an NMR spectrometer. Although substantially enhanced NMR signals can be obtained, the single scan nature of this technique a priori impedes the use of correlation experiments, which represent some of the most powerful applications of NMR spectroscopy. Here, an alternative method for multiscan spectroscopy from D-DNP samples utilizing a flow NMR probe is described. Multiple hyperpolarized segments of sample are sequentially injected using a purpose designed device. Hadamard spectroscopy can then be applied for obtaining chemical shift correlation information even from a small number of scans. This capability is demonstrated with a four-scan data set for obtaining the [C-13, H-1] correlations in the test molecule 1-butanol. Because of the effects of spin lattice relaxation and concentration gradients in the D-DNP experiment, the subtractive process for Hadamard reconstruction requires an additional step of intensity scaling. For this purpose, a reconstruction procedure was developed that uses entropy maximization and is robust with respect to noise and signal overlap. In a broader sense, the multiscan NMR as described here is amenable to various correlation NMR experiments, and increases the versatility of D-DNP in small-molecule characterization.