Molecular distances from dipolar coupled spin-labels: The global analysis of multifrequency continuous wave electron paramagnetic resonance data
Molecular distances from dipolar coupled spin-labels: The global analysis of multifrequency continuous wave electron paramagnetic resonance data
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DOI：
10.1016/s0006-3495(97)78832-5
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发表时间：
1997-04-01
影响因子：
3.4
通讯作者：
Beth, AH
中科院分区：
文献类型：
--
作者：
Hustedt, EJ;Smirnov, AI;Beth, AH
对于固定的氮氧化物自旋标记物与一个定义良好的探针间的几何形状，解决偶极分裂，可以观察到在连续波电子顺磁共振（CW-EPR）光谱为电子间的距离大至30埃，使用全氘代探针。在这项工作中，算法被开发用于计算CW-EPR光谱的固定化，偶极耦合氮氧自由基，然后用于定义灵敏度的限制，作为几何形状和微波频率的函数的电子间距离。其次，在9.8、34和94 GHz收集了N-6-自旋标记的辅酶NAD（+）与微晶四聚甘油醛-3-磷酸脱氢酶（GAPDH）结合的CW-EPR谱。这些数据已经进行了分析，使用模拟退火和全局分析的组合，以获得一个独特的适合的数据。定义两个氮氧化合物的相对取向的internitroxide距离和五个角度的值是在合理的协议与从已知的晶体结构建立的分子模型。最后，利用基于布朗动力学轨迹的算法研究了刚体各向同性转动扩散对偶极偶氮氧化合物CW-EPR谱的影响。这些计算表明，在存在刚体旋转扩散的情况下，CW-EPR谱对偶极耦合的敏感性。
For immobilized nitroxide spin-labels with a well-defined interprobe geometry, resolved dipolar splittings can be observed in continuous wave electron paramagnetic resonance (CW-EPR) spectra for interelectron distances as large as 30 Angstrom using perdeuterated probes. In this work, algorithms are developed for calculating CW-EPR spectra of immobilized, dipolar coupled nitroxides, and then used to define the limits of sensitivity to the interelectron distance as a function of geometry and microwave frequency. Secondly, the CW-EPR spectra of N-6-spin-labled coenzyme NAD(+) bound to microcrystalline, tetrameric glyceraldehyde-3-phosphate dehydrogenase (GAPDH) have been collected at 9.8, 34, and 94 GHz. These data have been analyzed, using a combination of simulated annealing and global analysis, to obtain a unique fit to the data. The values of the internitroxide distance and the five angles defining the relative orientation of the two nitroxides are in reasonable agreement with a molecular model built from the known crystal structure. Finally, the effect of rigid body isotropic rotational diffusion on the CW-EPR spectra of dipolar coupled nitroxides has been investigated using an algorithm based on Brownian dynamics trajectories. These calculations demonstrate the sensitivity of CW-EPR spectra to dipolar coupling in the presence of rigid body rotational diffusion.