Dynamic nuclear polarization (DNP) upgrade for solid-state NMR spectrometer (400 MHz)

动态核极化使NMR光谱的信号增强达到3个数量级。这一方面允许在几分钟或几小时内进行实验，否则需要几周或几个月的时间。另一方面，为NMR光谱学开辟了全新的应用领域，如果没有DNP，这些领域将无法进入。我们计划的研究旨在调查基本原理以及新型DNP方法的发展。通过对现有的400 MHz固态NMR光谱仪进行DNP升级，我们将能够进行多个方向的研究：在项目线A中，我们将开发基于顺磁性金属离子络合物的新型极化剂，并研究DNP的基本方面。新的极化剂可以通过自旋标记附着到感兴趣的（大）分子或表面上，或者可以通过掺杂直接掺入分析物相中。此外，我们将调查的直接DNP转移的距离依赖性，以及通过在电子自旋附近的自旋扩散的中继转移。这些主题在实现项目线B的主要目标-具体地点的自然人处理增强方面发挥着关键作用。在这里，我们希望在与极化剂的电子自旋或复杂混合物中感兴趣的特定组分的电子自旋的一定距离内实现核自旋的特定极化增强。为此，我们将研究三种情况：（i）DNP活性金属离子特异性地或内源性地结合在大分子内;（ii）DNP活性自旋标记结合到靶分子上;（iii）引入（抗磁性）间谍功能，其通过动力学诱导的交叉弛豫（SCREAM-DNP）在核自旋上特异性地产生超极化。在项目线C中，我们将最终将DNP增强NMR光谱应用于生物分子和材料科学的有趣问题。我们的目标是主题，包括聚合物在溶液中的结构或折叠，在配合物或表面上结合的配体的特定NMR光谱，在具有天然同位素丰度的化合物中的时间分辨分子切换，以及迄今未知的多相催化机制的调查。

Dynamic nuclear polarization enables a tremendous signal enhancement for NMR spectroscopy of up to 3 orders of magnitude. This allows on the one hand to perform experiments within minutes or hours which otherwise would take weeks or months of time. On the other hand, completely new fields of application are opened for NMR spectroscopy which would not be accessible without DNP. Our planned research aims towards the investigation of basic principles as well as the developments of novel DNP methods. This will allow for new techniques to structurally characterize biomolecules and materials.By the installation of a DNP upgrade for our existing 400 MHz solid-state NMR spectrometer we will be able to pursue several directions of research: In project line A we will develop new polarizing agents based on paramagnetic metal ion complexes and investigate fundamental aspects of DNP. New polarizing agents can be attached to (macro-)molecules or surfaces of interest via spin labeling or can be directly incorporate into analyte phases via doping. Furthermore, we will investigate the distance dependence of the direct DNP transfer as well as of the relayed transfer via spin diffusion in the immediate vicinity of the electron spin. These topics play a critical role in achieving site-specific DNP enhancement which is the main aim of project line B. Here, we want to achieve the specific polarization enhancement of nuclear spins within a certain distance to the electron spin of the polarizing agent or of a specific component of interest within a complex mixture. For this we will investigate three scenarios: (i) a DNP-active metal ion is specifically or endogenously bound within a macromolecule; (ii) a DNP-active spin label is bound to a target molecule; (iii) a (diamagnetic) spy function is introduced which specifically creates hyperpolarization on nuclear spins via dynamics-induced cross relaxation (SCREAM-DNP). In project line C we will finally apply DNP-enhanced NMR spectroscopy on interesting questions of biomolecular as well as of materials science. We aim at topics including the structure or folding of polymers in solution, the specific NMR spectroscopy of ligands bound in complexes or on surfaces, the time-resolved molecular switching in compounds with natural isotope abundance, as well as the investigation of hitherto unknown mechanisms in heterogeneous catalysis.