Pulsed electron-electron double resonance spectroscopy between a high-spin Mn(2+) ion and a nitroxide spin label.
Pulsed electron-electron double resonance spectroscopy between a high-spin Mn(2+) ion and a nitroxide spin label.
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DOI：
10.1039/c4cp05362a
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发表时间：
2015-02
期刊：
影响因子：
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通讯作者：
D. Akhmetzyanov;J. Plackmeyer;B. Endeward;V. Denysenkov;T. Prisner
中科院分区：
文献类型：
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作者：
D. Akhmetzyanov;J. Plackmeyer;B. Endeward;V. Denysenkov;T. Prisner
脉冲电子-电子双共振（PELDOR）在生物分子应用中引起了相当大的关注，因为它提供了在1.5-8 nm范围内的自旋标记对之间的距离的精确测量。通常，通过用半胱氨酸残基定点自旋标记掺入的氮氧部分用作蛋白质系统中的自旋探针。最近，天然存在的辅因子和金属离子也被探索为用于这种测量的顺磁自旋物种。在这项工作中，我们研究了PELDOR的性能之间的氮氧自由基自旋标记和高自旋Mn（2+）离子在合成的模型化合物在Q波段（34 GHz）和G波段（180 GHz）。我们表明，与高频PELDOR获得的距离是在良好的协议与结构预测。在Q波段的频率下，通过探测高自旋Mn（2+）离子或氮氧自旋标记进行了实验。在G-波段频率，我们已经能够检测到偶极振荡频率的变化，这取决于跨g-张量分辨氮氧EPR谱的泵浦-探测位置。这些变化是由于模型化合物中氮氧自旋标记的流动性受限所致。我们的研究结果表明，高自旋Mn（2+）离子可用于精确的距离测量，并为许多生物学应用打开大门，因为天然存在的Mg（2+）位点可以很容易地交换为Mn（2+）。
Pulsed Electron-Electron Double Resonance (PELDOR) has attracted considerable attention for biomolecular applications, as it affords precise measurements of distances between pairs of spin labels in the range of 1.5-8 nm. Usually nitroxide moieties incorporated by site-directed spin labelling with cysteine residues are used as spin probes in protein systems. Recently, naturally occurring cofactors and metal ions have also been explored as paramagnetic spin species for such measurements. In this work we investigate the performance of PELDOR between a nitroxide spin label and a high-spin Mn(2+) ion in a synthetic model compound at Q-band (34 GHz) and G-band (180 GHz). We demonstrate that the distances obtained with high-frequency PELDOR are in good agreement with structural predictions. At Q-band frequencies experiments have been performed by probing either the high-spin Mn(2+) ion or the nitroxide spin label. At G-band frequencies we have been able to detect changes in the dipolar oscillation frequency, depending on the pump-probe positions across the g-tensor resolved nitroxide EPR spectrum. These changes result from the restricted mobility of the nitroxide spin label in the model compound. Our results demonstrate that the high-spin Mn(2+) ion can be used for precise distance measurements and open the doors for many biological applications, as naturally occurring Mg(2+) sites can be readily exchanged for Mn(2+).