High-field Dynamic Nuclear Polarization Magic Angle Spinning NMR for Chemistry, Physics, Materials, Pharmaceuticals and Biomolecular Science

固体核磁共振是一种光谱技术，用于研究从用于储氢、药物输送和催化的先进材料到生物分子(如蛋白质和RNA)的分子结构和动力学。然而，与其他方法相比，固态核磁共振具有灵敏度低、信号积累采集时间长或需要大样本量等缺点。在核磁共振实验中获得的信号量取决于在磁场存在时产生的核自旋极化，由于原子核的磁矩相对较弱，因此需要超导磁体。然而，即使有当今最强大的超导磁体，也不可能对稀薄物种进行核磁共振研究，例如吸附在表面的分子、整个细胞中的蛋白质或自然丰度较低的同位素。然而，电磁磁矩大约比氢核强三个数量级，因此自由基中未配对的电子携带更大的自旋极化。因此，核磁共振信号可以通过所谓的动态核极化(DNP)来增强，动态核极化涉及通过相互偶极耦合将注入样品中的自由基的大电子极化转移到相邻的核上。DNP过程需要使用强微波源使电子自旋共振谱中的特定频率饱和。DNP的原理从核磁共振早期就已为人所知，但这项技术仅限于比现代核磁共振光谱仪中使用的磁场小得多的磁场，这对化学中心的解析具有严重影响。然而，回旋管作为高功率微波源的发展使在高频下运行的强大的DNP仪器成为可能。现在可以实现高达300倍的信号增强，相应地所需测量时间减少了100000倍。最近DNP硬件的商业化使其有可能专注于广泛的科学学科中的应用，而不必担心复杂的仪器要求。该提案旨在通过在诺丁汉大学安装基于商业仪器的DNP设施，为英国科学界的广泛部门提供访问DNP固态核磁共振的途径。

Solid-state nuclear magnetic resonance (NMR) is a spectroscopic technique which is used to study the molecular structure and dynamics of systems from the advanced materials used for hydrogen storage, drug delivery and catalysis to biological molecules, such as proteins and RNA. However, compared to other approaches, solid-state NMR suffers from a lack of sensitivity and long acquisition times for signal accumulation or large sample volumes are required. The amount of signal acquired in a NMR experiment depends on the nuclear spin polarization which arises in the presence of a magnetic field, and since the magnetic moments of nuclei are relatively weak, a superconducting magnet is required. However, even with the strongest superconducting magnets available today, NMR studies of dilute species, such as molecules adsorbed on surfaces, proteins in whole cells or isotopes with low natural abundance, are impossible.However, the electronic magnetic moment is about three orders of magnitude stronger than that for the hydrogen nucleus and consequently unpaired electrons in radicals carry a much larger spin polarization. Hence, the NMR signal can be enhanced by so-called dynamic nuclear polarization (DNP) which involves the transfer of the large electronic polarization from radicals implanted in the sample onto neighbouring nuclei via their mutual dipolar coupling. The DNP process requires the saturation of particular frequencies in the electron spin resonance spectrum using a strong microwave source. The principles of DNP have been known since the early days of NMR, but the technique was limited to magnetic fields much smaller than those used in modern NMR spectrometers with severe implications for the resolution of chemical sites. However, the development of gyrotrons as high-power microwave sources has made robust DNP instrumentation operating at high frequencies possible. Signal enhancements of up to 300-fold can now be achieved, corresponding to a reduction of a factor of 100000 in the required measuring time. The recent commercialization of DNP hardware makes it possible to focus on applications in a wide range of scientific disciplines rather than having to worry about the complex instrumental requirements.This proposal aims to provide access to DNP solid-state NMR for a broad section of the UK science community by installing a DNP Facility at the University of Nottingham based on a commercial instrument.