Renewing the Warwick 600 MHz Solid-State NMR System: Enabling State of the Art Technique Development and Novel Structural Applications

当科学家调查问题时，就像所有优秀的侦探一样，他们需要关于正在发生的事情的线索。对于一系列关键问题，能够揭示原子周围局部环境的技术对于在这一层面上提供对结构的洞察至关重要，这往往支配着材料或分子的行为。核磁共振(核磁共振)谱在整个科学界变得越来越重要，因为它是一种元素特定的探针，可以区分不同位置环境中非常微小的变化(例如，结构中SiO4单元连接的角点数，或碳的不同成键，如CH3和CH2之间的差异)。核磁共振利用了原子核固有的磁性：就像指南针在地球磁场中的对准一样，核磁体在强磁场中有一个更好的方向。然而，这种偏好是微弱的，通过施加共振无线电波，即其频率和能量与翻转核磁体所需的能量精确匹配，可以使核磁体的方向从例如对准磁场改变为对准磁场。原子核周围的电子也会受到磁场的影响。重要的是，特定原子核的共振频率非常敏感地依赖于电子的这种额外反应，因此原子核充当局部电子环境的间谍，因此特定的化学键使其能够用于探测环境，如上所述。不同核同位素的共振频率被很好地分开，使得核磁共振光谱是特定于特定选择的同位素的。(一种元素可以以不同的同位素存在，因此原子核中的质子数量相同，但中子数量不同--该数量指的是质子和中子的总数。)该项目将利用元素周期表的大部分内容。有些核很容易(如13C和29Si)，而另一些则很少用核磁共振观察到(如33S，47，49Ti)。该项目旨在提供最先进的设备，以便实施最新的、现代的实验和设计新的实验。该设备将与高磁场一起使用，这使得一些在较低磁场下不可能进行的实验成为可能，因为该系统将提供更高的分辨率和更大的信号。核磁共振的关键优点之一是原子核经历了相互作用，传达了关于其周围环境的准确信息。作为一个例子，偶极相互作用的产生是因为核磁铁并不是孤立的，而是以一种类似于两个条形磁铁在靠近时如何吸引或排斥的方式相互作用。重要的是，这种所谓的偶极相互作用的大小与两个核自旋之间的立方距离成反比。因此，测量一对17O和1H原子核之间的这种偶极相互作用可以直接得出一个氧原子和一个氢原子之间的距离。这样的距离可以用来量化氢键的程度--氢键的相互作用在确定蛋白质的三维结构方面起着关键作用。对一项好技术的测试是，它适用于广泛的问题。作为该项目的一部分开发的设备和技术将同时应用于物理科学和生命科学。原子级结构信息将应用于的问题包括：药物、碳氢化合物转化催化剂、火山材料、放射性废物储存玻璃、新的组织替代材料、了解疾病和酶途径以及新的电子材料。正是通过基于问题的科学家和基于技术的科学家之间的伙伴关系，才取得了真正的进展。

When scientists investigate problems, like all good detectives they need clues as to what is happening. For a whole range of key problems, techniques that can reveal the local environment around an atom are crucial to provide insight into the structure at this level, which often governs how a material or molecule behaves. Nuclear Magnetic Resonance (NMR) spectroscopy has increased in importance throughout the sciences as it is an element specific probe that can distinguish very small changes in the surroundings of different sites (e.g. the number of corners by which an SiO4 unit is connected in a structure, or the different bonding of carbon, such as the differences between CH3 and CH2). NMR exploits the inherent magnetism of atomic nuclei: like the alignment of a compass needle in the Earth's magnetic field, nuclear magnets have a preferred direction when placed in a strong magnetic field. This preference, however, is weak and a nuclear magnet can be made to change its direction from e.g. aligned with to aligned against the magnetic field, by applying a resonant radio wave, i.e., one whose frequency and hence energy matches precisely the energy required to flip the nuclear magnet. The electrons surrounding the atomic nucleus are also affected by the presence of a magnetic field. Importantly, the resonant frequency of a particular nucleus depends very sensitively on this additional response of the electrons, such that the atomic nuclei act as spies of the local electron environment and hence the specific chemical bonding allowing it to be used to probe environments as described above.The resonant frequencies of different nuclear isotopes are well separated such that an NMR spectrum is specific to a particular chosen isotope. (An element can exist as different isotopes whereby there is the same number of protons but a different number of neutrons in the nucleus - the number refers to the total number of protons and neutrons.) This project will make use of much of the Periodic Table. Some nuclei are easy (such as 13C and 29Si) but others have been rarely observed by NMR (e.g. 33S, 47,49Ti). The project is to provide the state of the art equipment to allow the latest, modern experiments to be implemented and new ones designed. The equipment will be used in conjunction with a high magnetic field, and this makes possible some experiments that are not possible at lower fields because of the increased resolution for some nuclei and larger signal that the system will provide. One of the key plus points for NMR is that nuclei experience interactions that convey precise information about their surroundings. As an example the dipole interaction arises as the nuclear magnets are not isolated, but rather they interact in an analogous way to how two bar magnets either attract or repel when brought close together. Importantly, the magnitude of this so-called dipolar interaction is inversely proportional to the cubed distance between the two nuclear spins. Thus, the measurement of such dipolar interactions between a pair of say 17O and 1H nuclei directly gives the distance between an oxygen and a hydrogen atom. Such a distance can be used to quantify the degree of hydrogen bonding - an interaction that plays a key role in determining, e.g., the three-dimensional structure of a protein.A test of a good technique is that it is applicable to a wide range of problems. The equipment and the techniques developed as part of this project will be applied to both physical and life sciences. Problems to which the atomic scale structural information will be applied include: pharmaceuticals, catalysts for hydrocarbon conversion, volcanic materials, radioactive waste-storage glasses, new tissue replacement materials, understanding diseases and enzyme pathways and new electronic materials. It is through the partnership between problem-based and technique-based scientists that real progress is made.