Solid-state NMR of unreceptive nuclei

固体核磁共振是在分子水平上探测固体材料的结构和动力学的最强大的技术之一。虽然大多数核磁共振用于有机分子中元素的同位素(例如，1H、13C、15N等)，但也可以研究许多其他具有核磁共振活性的核素。我们的研究小组专门研究了整个元素周期表中的核素的SS核磁共振，包括自旋1/2的核(如89Y，109Ag，195Pt，207Pb等)。和四极(自旋&GT；1/2)核(如14N，35Cl，49Ti，65Cu，91Zr)；后一类约占元素周期表中具有核磁共振活性的核的73%。这些核中的许多被归类为不可接受的，这意味着它们的研究非常具有挑战性，因为(1)低的核磁共振频率，(2)低的自然丰度，(3)大的各向异性核磁共振相互作用产生的广泛模式，(4)不方便的弛豫特性或(5)它们的组合。 我的团队使用SS核磁共振作为主要技术，以及X射线衍射和量子化学计算来解决各种问题。特别是，我们致力于开发方法来有效地获取其中许多核素的SS核磁共振谱，因为它们在化学、生物和物理的许多领域都是如此重要。我们应用我们的新方法来研究各种材料，包括(1)用于生产聚合物的多相催化剂，(2)多肽、生物聚合物和其他生物分子，以及(3)固体药物及其多晶型，它们是纯固体物质的不同相，由至少两种不同的原子排列产生。最后一个问题特别有趣，因为我们应用基础科学来了解核磁共振参数和分子结构之间的关系，并利用这一点来解决与制药行业及其消费者密切相关的问题：即如何区分药物成分的晶型，以便我们可以了解什么分子相互作用可以改善稳定性、货架期和生物利用度。此外，每一种晶型都是可申请专利的，因此我们可以帮助保护知识产权和有价值的专利。

Solid-state nuclear magnetic resonance (SSNMR) is one of the most powerful techniques available for probing structure and dynamics in solid materials at the molecular level. While the majority of NMR is applied to isotopes of elements found in organic molecules (e.g., 1H, 13C, 15N, etc.), there are many other NMR-active nuclides that can be investigated. Our research group specializes in SSNMR of nuclides across the periodic table, including spin-1/2 nuclei (e.g., 89Y, 109Ag, 195Pt, 207Pb, etc.) and quadrupolar (spin > 1/2) nuclei (e.g., 14N, 35Cl, 49Ti, 65Cu, 91Zr); this latter category constitutes ca. 73% of the NMR-active nuclei in the periodic table. Many of these nuclei are classified as unreceptive, meaning that they are very challenging to study due to (i) low NMR frequencies, (ii) low natural abundance (iii) broad patterns arising from large anisotropic NMR interactions, (iv) inconvenient relaxation characteristics or (v) combinations thereof. My group utilizes SSNMR as the primary technique, along with X-ray diffraction and quantum chemical computations to solve a variety of problems. In particular, we work on development of methodologies to efficiently acquire SSNMR spectra of many of these nuclides, since they are so important in many areas of chemistry, biology and physics. We apply our new methodologies to study a variety of materials, including (1) heterogeneous catalysts used to produce polymers, (2) polypeptides, biopolymers and other biological molecules, and (3) solid pharmaceuticals and their polymorphs, which are distinct phases of a pure solid substance resulting from at least two differing arrangements of atoms. The last problem is particularly interesting, since we apply fundamental science to understand the relationship between NMR parameters and molecular structure, and use this to solve a problem of great relevance to the pharmaceutical industry and its consumers: i.e., how to differentiate polymorphs of pharmaceutical ingredients, so that we may understand what molecular interactions may lead to improved stability, shelf-life and bioavailability. In addition, each polymorph is patentable, so we may aid in the protection of intellectual property and valuable patents.