Three-spin correlations in double electron-electron resonance
Three-spin correlations in double electron-electron resonance
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DOI：
10.1039/b905724b
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发表时间：
2009-01-01
影响因子：
3.3
通讯作者：
Godt, Adelheid
中科院分区：
文献类型：
--
作者：
Jeschke, Gunnar;Sajid, Muhammad;Godt, Adelheid
脉冲电子顺磁共振技术的距离测量越来越多地应用于包含两个以上自旋标签的系统。在典型的实验条件下，这导致偶极频率的和和差组合对信号的贡献。由于这些贡献在数据分析中使用的表达式中被忽略，它们会导致距离分布中的伪影。结果表明，这些伪影导致了距离分布的大幅度扩大。通过测量具有可变反转效率的双电子-电子共振（DEER）数据，并用适当的多项式拟合每个时间点的数据，可以将对贡献与三自旋贡献分离开来。对具有等边三角形几何结构的构象不变三基和相应的具有相同旋距的双基的实验表明，该方法可以显著改善距离分布。三个自旋的贡献显示了自旋-自旋矢量之间角度的信息。通过将一般三角模型同时拟合到偶极光谱和三旋贡献上，分析了一系列具有等边、等腰和不等边三角形几何结构的三基的数据。与预期三角形边长的一致是令人满意的。
Distance measurements by pulse electron paramagnetic resonance techniques are increasingly applied to systems that contain more than two spin labels. Under typical experimental conditions this leads to signal contributions from sum and difference combinations of dipolar frequencies. As these contributions are neglected in the expressions used in data analysis they cause artifacts in distance distributions. It is shown that the artifacts lead to substantial broadening of the distance distribution. By measuring double electron-electron resonance (DEER) data with variable inversion efficiency of the pump pulse and fitting the data at each point in time by appropriate polynomials the pair contribution can be separated from the three-spin contribution. Experiments on a conformationally invariant triradical with equilateral triangle geometry and the corresponding biradical with the same interspin distance demonstrate that this approach leads to a considerable improvement in the distance distribution. The three-spin contribution is shown to provide information on angles between spin-spin vectors. Data for a series of triradicals with equilateral, isosceles, and scalene triangle geometry are analysed by fitting a general triangle model simultaneously to the dipolar spectra of the pair and three-spin contribution. The agreement with the expected side lengths of the triangles is satisfying.