Nanometre distance measurements with EPR using different spin probes.

脉冲电子顺磁共振(EPR)谱是一种新兴的远距离测量技术。稀疏的长程距离对于理解复杂纳米结构的结构和灵活性是非常有价值的。具体地说，使用名为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的距离，最大可达10 nm，甚至更远。这些顺磁中心可以是天然的金属离子或自由基辅因子，但最常见的是通过一种称为位置定向自旋标记的技术故意引入它们。该项目旨在探索可用于自旋标记的不同类型的顺磁中心，并牢固地建立标记选择的最佳做法，特别是关于可以从用几个光谱不同的探针标记的样本中提取的信息量(正交标记)。为此，将采用含有顺磁性金属中心和有机基团的化学模型，使用基于两个频率激发的不同方法(PELDOR)或基于松弛的方法(RIDME)对金属氮氧化物的距离测量进行基准测试。在第二步中，将仔细审查带有多个自旋中心的系统。这对于在多聚体系中的应用非常有价值，在该体系中，几个自旋标记的单体组装到功能单元上。特别是，解决复杂结构中的特定距离将是信息的巨大收益。这些模型研究将得到数值模拟的支持，并设想将结果转移到蛋白质多聚体模型上。这种方法将增加结构性EPR技术的武器库，其长期目标是识别用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.