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

动态核极化使核磁共振光谱的信号增强高达3个数量级。这一方面允许在几分钟或几小时内完成实验，否则将需要几周或几个月的时间。另一方面，开辟了核磁共振波谱学的全新应用领域，这是没有DNP无法实现的。我们计划的研究目标是对基本原理的调查以及新的DNP方法的发展。这将允许新技术在结构上表征生物分子和材料。通过为我们现有的400 MHz固态核磁共振光谱仪安装DNP升级，我们将能够追求几个研究方向：在项目线a中，我们将开发基于顺磁性金属离子配合物的新型极化剂，并研究DNP的基本方面。新的极化剂可以通过自旋标记附着在（大分子）或感兴趣的表面上，也可以通过掺杂直接掺入分析物相中。此外，我们将研究直接DNP转移的距离依赖关系，以及在电子自旋附近通过自旋扩散进行的中继转移。这些主题在实现特定位点的DNP增强方面发挥着关键作用，这是项目线b的主要目标。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活性金属离子在大分子内特异性或内源性结合；（ii） dnp活性自旋标签与目标分子结合；（iii）引入了一个（反磁）间谍函数，该函数通过动态诱导的交叉弛豫（SCREAM-DNP）在核自旋上产生超极化。在项目线C中，我们将最终将dnp增强核磁共振波谱应用于生物分子和材料科学的有趣问题。我们的目标主题包括聚合物在溶液中的结构或折叠，结合在配合物或表面上的配体的特定核磁共振波谱，具有天然同位素丰度的化合物的时间分辨分子开关，以及迄今为止未知的多相催化机制的研究。

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.