A Millimeter-wave Tunable Cavity for Ultra-sensitive Solids and Liquids DNP-NMR at Low Budget

 描述（由申请人提供）：NMR可能是用于所有类型分子的结构测定和功能阐明的最强大和最广泛使用的分析技术，但其灵敏度低，特别是对于不溶性生物大分子。动态核极化（DNP）与魔角自旋（MAS）最近已证明S/N增益超过两个数量级，在~100 K相比，传统的MAS-NMR在许多生物固体。尽管这对生物医学研究有巨大的好处，但DNP的适应率将受到其非常高的价格标签（目前 1.8 - 4 M美元），主要是因为特殊的磁铁（扫描线圈）和昂贵的回旋管所需的，由于目前的DNP探针的微波效率非常差。我们对一种新型毫米波DNP腔的详细模拟表明，在相同的B 0和温度下，对于类似体积（1-25 μ L）的样品，微波功率比现有的MAS-DNP设计低两个数量级，就有可能实现所需的电子自旋饱和。所提出的新型DNP腔最初仅与静态（非旋转）方法兼容，并且静态固体NMR技术的线宽总是比MAS大得多。然而，静态高功率的方法，如PISEMA，已作为卓有成效的MAS方法在产生大的，复杂的，螺旋膜蛋白的结构，因为独特的能力，提供相关的偶极和各向异性的化学位移数据需要解决的符号简并。由NCSU合作团队开发的含有宏观对齐和水合膜蛋白的纳米结构基底的新型叠板腔体布置显著降低了样品加热，即使对于RT或接近RT的有损耗液体样品，也能显著提高光谱分辨率。受静态DNP腔的启发，与MAS-DNP兼容的相关腔设计也将被模拟。静态DNP腔和探针，将最初开发的7 T预计将产生两个数量级的增益，在S/N为广泛的固体NMR实验，它将这样做的两个数量级低毫米波功率比竞争的MAS-DNP设计。这将使几乎所有当前NMR团队都有可能将静态H/X/Y/e-DNP能力带入他们的实验室-固体和液体-总入门预算低于15万美元，包括0.05-0.3 W mmw源，DNP探针，波导和过渡-所有可扩展到非常高的领域。Doty静态DNP腔的开发可以使全球进行DNP NMR的团队数量在未来四到八年内从少数增加到数百个。总的来说，拟议的技术开发预计将为生物医学研究人员提供膜蛋白和细胞膜系统的结构-功能研究的巨大新机会。

 DESCRIPTION (provided by applicant): NMR is probably the most powerful and widely used analytical technique for structure determination and function elucidation of molecules of all types, but it suffers from low sensitivity, particularly for insoluble biological macromolecules. Dynamic Nuclear Polarization (DNP) with Magic Angle Spinning (MAS) has recently demonstrated S/N gains exceeding two orders of magnitude at ~100 K compared to conventional MAS-NMR in many biological solids. Despite this enormous benefit to biomedical research, the adaptation rate of DNP will be severely limited by its very high price tag (currently $1.8-4M), mostly because of the special magnet (with sweep coils) and expensive gyrotron required, owing to the very poor microwave efficiency of current DNP probes. Our detailed simulations of a novel millimeter wave (mmw) DNP cavity have shown the potential for achieving the needed electron spin saturation with two orders of magnitude lower microwave power than the existing MAS-DNP designs for samples of similar volume (1-25 L) at the same B0 and temperature. The proposed novel DNP cavity is initially compatible only with static (non-spinning) methods, and the linewidths from static solids NMR techniques are always much greater than in MAS. However, static high-power methods, such as PISEMA, have been as fruitful as MAS methods in yielding structures of large, complex, helical membrane proteins because of the unique capability to provide correlated dipolar and anisotropic chemical shift data needed to resolve sign degeneracies. A novel stacked-plate cavity arrangement of nanostructured substrate containing macroscopically aligned and hydrated membrane proteins developed by collaborating NCSU team dramatically reduces sample heating enabling substantial DNP S/N enhancements even for lossy liquid samples at or near RT with substantially improved spectral resolution. Related cavity designs compatible with MAS-DNP, inspired by the static-DNP cavity, will also be simulated. The static DNP cavity and probe that will be initially developed for 7 T is expected to yield two orders of magnitude gain in S/N for a wide range of solids NMR experiments, and it will do so with two orders of magnitude lower mmw power than competing MAS-DNP designs. This will make it possible for virtually all current NMR groups to bring static H/X/Y/e- DNP capabilities into their labs - for both solids and liquids - for a total entry budget of under $150K, including the 0.05-0.3 W mmw source, DNP probe, waveguides, and transitions - all scalable to very high fields. Development of the Doty static-DNP cavity could allow the number of groups doing DNP-NMR worldwide to increase from a handful to hundreds over the next four to eight years. Overall, the proposed technology development is expected to provide biomedical researchers with tremendous new opportunities for the structure-function studies of membrane proteins and cellular membrane systems.