Sensitivity-Enhanced High-Field Solution-State NMR by Gyrotron-Driven DNP

核磁共振是表征分子结构和动力学的最重要和最广泛使用的方法之一，但它的灵敏度--特别是当应用于液体样品时--对于许多重要的应用是不够的。在化学系化学测量与成像计划的支持下，佛罗里达州立大学国家强磁场实验室(NHMFL)的Sungsool Wi、Lucio Frydman和Stephen Hill博士正在努力实现溶液状态的适用性，以适应最近的技术和概念突破，这些突破显著提高了高场核磁共振对固体表征的灵敏度。延伸到液体(包括水溶液)可能会对化学和生物化学产生革命性的影响，特别是在表征有限数量的小到中型分子方面。潜在的应用包括天然产品和药物化学；石油和聚合物分析化学；食品和环境科学；以及代谢组学。NHMFL设置促进了技术的广泛传播，并为不同应用领域的外部用户提供了访问权限。Wi集团正在为高磁场(=14.1T/600 MHz)下的大容量样品(100 Ul)开发解决方案状态Overhauser增强的动态核极化(ODNP)核磁共振，旨在使用常规和低温冷却的溶液状态核磁共振探头显著提高典型条件下的核磁共振灵敏度。这项研究利用了最近开发的工作在395 GHz的高功率回旋源和匹配的准光学技术，以及包含定制核磁共振探头的600 MHz核磁共振溶液状态光谱仪。通过采用新的硬件，可以在低粘度、低介电损耗的溶剂(如正己烷)、超临界流体和使用新的自由基组合中进行ODNP增强的双共振实验，这些突破正在扩展到更广泛的有机分析物。原位EPR波谱在相同的600 MHz光谱仪中执行，并通过修改现有的准光接口实现，正被用于提供独特的机械见解并进一步优化这些ODNP增强的核磁共振实验。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Nuclear magnetic resonance (NMR) is one of the most important and widely used methods for characterizing molecular structure and dynamics, but its sensitivity - especially when applied to liquid samples - is inadequate for many important applications. With support from the Chemical Measurement & Imaging program in the Division of Chemistry, Drs. Sungsool Wi, Lucio Frydman, and Stephen Hill at Florida State University's National High Magnetic Field Laboratory (NHMFL) are working to achieve solution-state applicability for recent technological and conceptual breakthroughs that have dramatically improved the sensitivity of high-field NMR for characterization of solids. Extension to liquids (including aqueous solutions) may have transformative consequences in chemistry and biochemistry, particularly for characterizing limited quantities of small to medium-sized molecules. Potential applications include natural products and pharmaceutical chemistry; petroleum and polymer analytical chemistry; food and environmental sciences; and metabolomics. The NHMFL setting facilitates wide dissemination of the techniques, and provides accessibility to outside users in diverse application areas. It also enables extensive outreach efforts targeting high school students and involvement of undergraduates.The Wi group is developing solution-state Overhauser-enhanced dynamic nuclear polarization (ODNP) NMR for large volume samples ( 100 uL) at high magnetic fields (= 14.1 T/600 MHz), aiming to dramatically improve NMR sensitivity under typical conditions using conventional and cryogenically-cooled solution-state NMR probe heads. The research leverages the recent development of a high-power Gyrotron source operating at 395 GHz, with matching quasi-optical technologies, and a 600 MHz NMR solution-state spectrometer incorporating a customized NMR probe. These breakthroughs are being extended to a far wider range of organic analytes by employing new hardware which enables ODNP-enhanced double-resonance experiments in low-viscosity, low-dielectric-loss solvents such as hexane, in supercritical fluids, and using novel radical combinations. In situ EPR spectroscopy, executed in the same 600 MHz spectrometer and enabled through modifications to the existing quasioptical interface, is being employed to provide unique mechanistic insights and to further optimize these ODNP-enhanced NMR experiments.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.