Development of new 17O NMR spectroscopic techniques for studying biological systems

核磁共振波谱是研究分子结构、动力学和化学键的一种强大的分析技术。在过去的几十年里，这项技术的发展已经彻底改变了化学和生物科学。然而，大多数成功的生物系统的核磁共振研究，如蛋白质和核酸，主要是基于检测原子核自旋量子数为1/2的原子核，如1H， 13C和15N。另一方面，氧元素作为有机和生物分子中最丰富的元素之一，还没有被核磁共振光谱所探测到。这主要是因为唯一的核磁共振活性氧同位素17O的核自旋量子数为5/2（称为四极核）。此外，17O的天然丰度极低，为0.037%。众所周知，四极核很难用核磁共振来研究，因为它们通常会产生非常宽的核磁共振信号。因此，在生物大分子的背景下，17O通常被认为是“核磁共振不可见的”。最近，我们在解决这一难题的道路上取得了两个突破。首先，我们开发了新的核磁共振方法，可以检测固态和水溶液中生物大分子的高分辨率17O核磁共振光谱。其次，我们已经证明了将17O与营养不良的大肠杆菌菌株结合到重组蛋白中的一般方法。在未来5年，我们将把这些新方法应用于两种类型的生物系统：蛋白质和活的癌细胞。蛋白质的核磁共振光谱通常被认为是生物分子核磁共振的最后前沿。我们将探索17O NMR在蛋白质结构和动力学研究中所能提供的独特信息。我们将研究使用17O NMR作为一种新的示踪剂来监测活癌细胞中的葡萄糖和谷氨酰胺代谢。这将有助于建立17O NMR作为癌症诊断和监测的潜在有用的补充工具。我们研究计划的最终目标是使所有主要元素（氢、碳、氮和氧）在生物分子中发现，通过核磁共振波谱可以平等地访问。在这一领域，我们的研究项目一直处于国际领先地位。拟议研究的结果将对化学和生物科学的许多学科产生影响。拟议的研究计划还将为培养具有全球竞争力的下一代高素质人才提供极好的机会。

Nuclear magnetic resonance (NMR) spectroscopy is a powerful analytical technique for studying molecular structure, dynamics, and chemical bonding. The development of this technique over the past several decades has revolutionized chemical and biological sciences. However, most successful NMR studies of biological systems such as proteins and nucleic acids are primarily based on detection of atomic nuclei with a nuclear spin quantum number of 1/2 such as 1H, 13C, and 15N. On the other hand, the oxygen element, being one of the most abundant in organic and biological molecules, has not yet been accessible by NMR spectroscopy. This is principally because the only NMR-active oxygen isotope, 17O, has a nuclear spin quantum number of 5/2 (known as a quadrupolar nucleus). In addition, the natural abundance of 17O is extremely low, 0.037%. Quadrupolar nuclei are notoriously difficult to study by NMR because they often give rise to very broad NMR signals. As a result, 17O is very often considered to be "NMR invisible" in the context of biological macromolecules. Recently, we made two breakthroughs on the way of solving this challenging problem. First, we have developed new NMR methods that allow detection of high-resolution 17O NMR spectra for biological macromolecules both in the solid state and in aqueous solution. Second, we have demonstrated a general method of incorporating 17O into recombinant proteins with auxotrophic E. coli strains. In the next 5 years, we will apply these new methods to two types of biological systems: proteins and live cancer cells. 17O NMR spectroscopy of proteins is often considered to be the last frontier of biomolecular NMR. We will explore the unique information that 17O NMR can offer in the study of protein structure and dynamics. We will investigate the use of 17O NMR as a new tracer for monitoring glucose and glutamine metabolism in live cancer cells. This will help establish 17O NMR as a complementary tool potentially useful for cancer diagnosis and monitoring. The ultimate goal of our research program is to make all major elements (H, C, N, and O) found in biological molecules equally accessible by NMR spectroscopy. In this field, our research program has been an international leader. The outcomes from the proposed research will have impact in many disciplines in chemical and biological sciences. The proposed research program will also provide excellent opportunities for training of the next generation of highly qualified personnel to be competitive globally.