Suppression of ghost distances in multiple-spin double electron-electron resonance.
Suppression of ghost distances in multiple-spin double electron-electron resonance.
复制标题
DOI：
10.1039/c3cp44462g
复制
发表时间：
2013-03
期刊：
影响因子：
--
通讯作者：
Tona von Hagens;Y. Polyhach;M. Sajid;A. Godt;G. Jeschke
中科院分区：
文献类型：
--
作者：
Tona von Hagens;Y. Polyhach;M. Sajid;A. Godt;G. Jeschke
脉冲电子顺磁共振技术的距离测量越来越多地应用于多自旋系统。在双电子-电子共振实验中，两个以上的偶极耦合自旋表现为总调制深度的增加以及总和和差偶极频率贡献，这导致在距离分布中出现额外的峰，这些峰与系统的真实自旋间距离不对应，因此被称为幽灵贡献。这些鬼影的贡献可能如此显著，以至于它们可能被误认为真正的距离峰，或者真正的距离峰移动了位置或消失了。我们给出了一个简单的近似过程，通过在数据分析过程中操纵实验获得的形状因子，利用标度指数ζ(N)=1/(1-N)的简单幂标度来很大程度地抑制鬼影距离，其中N是系统中耦合自旋的数目。这种方法既不需要进一步的实验工作，也不需要关于标记和倒置效率的确切知识。这将使常规应用于生物系统成为可能。该方法在多达五个自旋的模拟测试用例上得到了验证，并应用于合成模型样本。用所提出的方法抑制鬼影距离对于对称几何和刚性分子效果最好，同时，这也是鬼影贡献最令人不安的情况。通过幂标度得到的距离分布与用先前获得的替代方法获得的分布是一致的，并且在某些情况下与真实的自旋间距离分布的预期非常一致。
Distance measurements by pulse electron paramagnetic resonance techniques are increasingly applied to multiple-spin systems. In the double electron-electron resonance experiment, more than two dipolar coupled spins manifest in an increased total modulation depth and in sum and difference dipolar frequency contributions that give rise to additional peaks appearing in the distance distribution, which do not correspond to the real interspin distances of the system and are hence referred to as ghost contributions. These ghost contributions may be so prominent that they might be mistaken for real distance peaks or that real distance peaks shift their position or disappear. We present a simple approximate procedure to suppress ghost distances to a great extent by manipulating the experimentally obtained form factor during data analysis by a simple power scaling with a scaling exponent ζ(N) = 1/(1-N), with N being the number of coupled spins in the system. This approach requires neither further experimental effort nor exact knowledge about labelling and inversion efficiency. This should enable routine application to biological systems. The approach is validated on simulated test cases for up to five spins and applied to synthetic model samples. The suppression of ghost distances with the presented approach works best for symmetric geometries and rigid molecules which, at the same time, are the cases where ghost contributions are most disturbing. The distance distributions obtained by power scaling are consistent with distributions that were obtained with previously obtained alternative approaches and agree, in some cases, strikingly well with the expectations for the true interspin distance distributions.