Nanometre distance measurements with EPR using different spin probes.

脉冲电子顺磁共振（EPR）光谱是一种新兴的远程距离测定技术。稀疏的远程距离对于理解复杂纳米结构的结构和灵活性非常有价值。具体来说，使用一种称为PELDOR（脉冲电子-电子双共振）或DEER（双电子-电子共振）的EPR方法，可以可靠地测量所研究系统中两个顺磁中心之间长达10纳米或更大的距离。这些顺磁中心可以是天然金属离子或自由基辅因子，但最常见的是，它们是通过一种称为定点自旋标记的技术故意引入的。该项目旨在探索不同类型的顺磁中心用于自旋标签，并牢固地建立标签选择的最佳实践，特别是关于可以从几个光谱不同探针标记的样品中提取的信息量（正交标记）。为此，将采用带有顺磁性金属中心和有机自由基的化学模型，采用基于两种频率激发（PELDOR）或基于弛豫（RIDME）的不同方法对金属氮氧化物距离测量进行基准测试。第二步，将仔细检查具有多个自旋中心的系统。这对于多聚体系统的应用是非常有价值的，其中几个自旋标记的单体组装成功能单元。特别是在复杂结构中处理特定距离将会获得巨大的信息。这些模型研究将得到数值模拟的支持，预计结果将转移到模型蛋白多聚体中。这种方法将增加结构EPR技术的军械库，其长期目标是确定当前方法无法获得的系统的结构变化。

Pulse electron paramagnetic resonance (EPR) spectroscopy is an emerging technique for long range distance determination. Sparse long-range distances are very valuable for understanding structure and flexibility of complex nanostructures. Specifically, using an EPR method called PELDOR (pulsed electron-electron double resonance) or DEER (double electron-electron resonance), it is possible to reliably measure distances of up to 10 nm and beyond between two paramagnetic centres in the system studied. These paramagnetic centres can be native metal ions or radical cofactors, but most commonly they are deliberately introduced by a technique called site-directed spin-labelling.This project aims to explore different types of paramagnetic centres to be employed a spin labels and to firmly establish best practices for the choice of labels especially with respect to the amount of information that can be extracted from samples labelled with several spectroscopically distinct probes (orthogonal labelling). To this end chemical models bearing paramagnetic metal centres and organic radicals will be employed to benchmark the metal nitroxide distance measurements using different methods based on excitation with two frequencies (PELDOR) or relaxation based methods (RIDME). In a second step systems bearing multiple spin centres will be scrutinised. This will be extremely valuable for applications in multimeric systems in which several spin-labelled monomers assemble to the functional unit. In particular addressing specific distances within the complex structure will be a huge gain in information. These model studies will be backed up by numeric simulations and the outcome is envisioned to be transferred to a model protein multimer. This approach will add to the armoury of structural EPR techniques with the long term aim of identifying structural changes in systems not accessible with current methods.