Pulsed EPR Dipolar Spectroscopy on Spin Pairs with one Highly Anisotropic Spin Center: The Low-Spin FeIII Case
Pulsed EPR Dipolar Spectroscopy on Spin Pairs with one Highly Anisotropic Spin Center: The Low-Spin FeIII Case
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DOI：
10.1002/chem.201902908
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发表时间：
2019-10-09
影响因子：
4.3
通讯作者：
Schiemann, Olav
中科院分区：
文献类型：
--
作者：
Abdullin, Dinar;Brehm, Philipp;Schiemann, Olav
脉冲电子顺磁共振（EPR）偶极光谱（PDS）提供了几种测量偶极耦合常数和电子自旋中心之间距离的方法。到目前为止，PDS测量大多应用于g各向异性适中的自旋中心，因此对偶极耦合常数的影响可以忽略不计。相反，具有大g各向异性的自旋中心产生依赖于g值的偶极耦合常数。在这种情况下，不能应用从原始PDS数据中提取距离的常用方法。本文以低自旋Fe3+离子为例，详细研究了g各向异性对PDS数据的影响。首先，利用Bedilo和Maryasov（苹果公司）的工作，从理论上描述了这种效应。粉剂。理由。2006,30,683-702)作为基础。然后，合成了两种已知的Fe3+/氮氧化物化合物和一种新的Fe3+/三烷基化合物，并利用弛豫诱导偶极调制增强（RIDME）方法对它们进行了PDS测量。在此基础上，开发了RIDME数据分析程序，从RIDME数据中提取出自旋间距离和相对于Fe3+ g张量系的自旋间矢量方向。通过与MD仿真的比较，验证了所确定的距离和方向的准确性。因此，该方法可以应用于高度相关的金属蛋白类，例如低自旋Fe3+离子。
Pulsed electron paramagnetic resonance (EPR) dipolar spectroscopy (PDS) offers several methods for measuring dipolar coupling constants and thus the distance between electron spin centers. Up to now, PDS measurements have been mostly applied to spin centers whose g-anisotropies are moderate and therefore have a negligible effect on the dipolar coupling constants. In contrast, spin centers with large g-anisotropy yield dipolar coupling constants that depend on the g-values. In this case, the usual methods of extracting distances from the raw PDS data cannot be applied. Here, the effect of the g-anisotropy on PDS data is studied in detail on the example of the low-spin Fe3+ ion. First, this effect is described theoretically, using the work of Bedilo and Maryasov (Appl. Magn. Reson. 2006, 30, 683-702) as a basis. Then, two known Fe3+/nitroxide compounds and one new Fe3+/trityl compound were synthesized and PDS measurements were carried out on them using a method called relaxation induced dipolar modulation enhancement (RIDME). Based on the theoretical results, a RIDME data analysis procedure was developed, which facilitated the extraction of the inter-spin distance and the orientation of the inter-spin vector relative to the Fe3+ g-tensor frame from the RIDME data. The accuracy of the determined distances and orientations was confirmed by comparison with MD simulations. This method can thus be applied to the highly relevant class of metalloproteins with, for example, low-spin Fe3+ ions.