New Direction in Nuclear Magnetic Resonance of Copper and Zinc Ions in Biological Systems

金属及其离子对生命是不可或缺的，因此，生物系统中超过三分之一的蛋白质需要金属离子的存在才能发挥作用。包括铜(铜)和锌(锌)在内的几种过渡元素已被证明是人体必需的，并以微量(从镁到克)的形式存在于体内。铜和锌都是生命所必需的，但毒性过大，因此必须严格控制它们的动态平衡。为了了解铜和锌在体内的作用，了解这两种金属离子在生物背景下所采用的结合化学和配位环境是非常重要的。遗憾的是，到目前为止，由于缺乏方便的物理和光谱性质来研究金属中心的局部结构和动力学，阻碍了对铜(I)和锌(II)生物化学的详细了解。核磁共振波谱可能是探索溶液中分子的结构和动力学的最强大的单一技术，因此，它从根本上促进了生物科学的进步。然而，在实践中，核磁共振对元素周期表中的几个元素，包括铜(I)和锌(II)的灵敏度很低，主要是因为它们具有核磁共振活性的稳定同位素的旋磁比很低，而且本质上信噪比很小。此外，这两个原子核都是四极核(自旋&GT；1/2)，导致共振线宽度在千赫范围内或超出可检测范围，这使得它不足以用于许多前沿科学应用。因此，有关含铜(I)和锌(II)的生物体系的溶液相核磁共振研究在文献中很少。*这项建议寻求资金，利用新建立的液态β-检测核磁共振(β-核磁共振)光谱，直接在几种金属离子络合物和金属蛋白中研究铜(I)和锌(II)金属结合部位的配位化学。贝塔核磁共振使用放射性同位素而不是稳定同位素，它允许通过检测极化的放射性离子发射的贝塔粒子来测量核磁共振信号。与传统的核磁共振波谱相比，它的灵敏度提高了1010，它可以应用于元素周期表中的许多元素，包括铜(I)和锌(II)。在过去的2-3年里，TRIUMF一直致力于加拿大TRIUMF的ISAC-I设施的液体β-核磁共振波谱仪的设计和实施。测试现在使用MG-31完成，毫不含糊地证明，β-核磁共振能够测量高质量的核磁共振，分辨率高于传统的MG-25核磁共振，在2-3 L的液体溶液中使用少至107个镁离子，不到一小时。鉴于最近的成就，我们现在已经准备好对不同的铜(I)和锌(II)结合的生物体系进行开创性的β-核磁共振测量。

Metals and their ions are indispensable for life, and as such more than one third of all proteins in biological systems require the presence of metal ions to function. Several transition elements, including copper (Cu) and zinc (Zn), have been proven to be essential for humans, and occur in the body at trace amounts (mg to g). Cu and Zn are both necessary for life, but toxic in excess, and therefore their homeostasis has to be tightly controlled. In order to understand the role of Cu and Zn in the body, it is of profound importance to understand the binding chemistry and the coordination environment that these two metal ions adopt in their biological context. Unfortunately, the absence of convenient physical and spectroscopic properties to study the local structure and dynamics at the metal sites has so far held back a detailed understanding of Cu(I) and Zn(II) biochemistry. ***Nuclear magnetic resonance (NMR) spectroscopy is probably the most powerful single technique to explore the structure and dynamics of molecules in solution, and therefore, it contributes fundamentally to the advancement of biological sciences. In practice, however, NMR suffers from poor sensitivity for several elements across the periodic table, including both Cu(I) and Zn(II), mainly because of the low gyromagnetic ratio of their NMR-active stable isotopes and intrinsically small signal-to-noise ratio. Furthermore, both nuclei are quadrupolar (spin > 1/2), leading to resonance lines widths in the kHz range or beyond detectability, which makes it inadequate for many frontier scientific applications. As a result, only a very few solution-phase NMR studies on Cu(I) and Zn(II)-containing biological systems can be found in the literature. ***This proposal seeks funds to investigate the coordination chemistry of Cu(I) and Zn(II) metal-binding sites directly in several metal ion complexes and metalloproteins using the newly established liquid-phase beta-detected NMR (beta-NMR) spectroscopy. Beta-NMR employs radioisotopes rather than stable isotopes, and it allows for measuring NMR signals by detecting the beta particles emitted by polarized, radioactive ions. It offers 1010 enhancement in sensitivity as compared to conventional NMR spectroscopy, and it can be applied to many elements across the periodic table, including both Cu(I) and Zn(II). For the past 2-3 years, TRIUMF has been working on the design and implementation of the liquid-phase beta-NMR spectrometer at the ISAC-I facility at TRIUMF, Canada. Testing is now completed using Mg-31, unambiguously establishing that beta-NMR is capable of measuring high-quality NMR resonances with resolution better than conventional Mg-25 NMR, using as few as 107 Mg ions in 2-3 L of liquid solution, and within less than an hour. Given the recent accomplishments, we are now well poised to conduct pioneering beta-NMR measurements on different Cu(I) and Zn(II) binding biological systems.