Sensitivity enhancement in pulse EPR distance measurements
Sensitivity enhancement in pulse EPR distance measurements
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DOI：
10.1016/j.jmr.2004.03.024
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发表时间：
2004-07-01
影响因子：
2.2
通讯作者：
Godt, A
中科院分区：
文献类型：
--
作者：
Jeschke, G;Bender, A;Godt, A
已建立的脉冲EPR方法用于测量电子自旋之间的小偶极-偶极耦合，依赖于恒定时间回波实验来分离偶极时间演化中的弛豫贡献。这需要在测量之前在灵敏度和分辨率之间做出妥协，因此只有在事先知道偶极子-偶极子耦合的大小以获得良好的近似值时才能获得最佳数据。此外，整个偶极演化函数的测量灵敏度相对较低。这些问题是克服了变时间实验，实现了抑制松弛贡献的参考反褶积。理论和实验结果表明，该方法可以显著提高典型系统和实验条件下的灵敏度。通过对时域数据进行矩阵氘化或数字长通滤波，可以进一步提高灵敏度或等效地扩大可访问距离范围。本文讨论了新的可变时间实验的优点和局限性，并将其与已建立的类似的恒定时间实验进行了比较，用于测量棒状持久双自由基的端到端距离为5和7.5 nm，以及用于测量植物光捕获复合物II的双自旋标记突变体中广泛分布的跨膜距离。(C) 2004爱思唯尔公司版权所有。
Established pulse EPR approaches to the measurement of small dipole-dipole couplings between electron spins rely on constant-time echo experiments to separate relaxational contributions from dipolar time evolution. This requires a compromise between sensitivity and resolution to be made prior to the measurement, so that optimum data are only obtained if the magnitude of the dipole-dipole coupling is known beforehand to a good approximation. Moreover, the whole dipolar evolution function is measured with relatively low sensitivity. These problems are overcome by a variable-time experiment that achieves suppression of the relaxation contribution by reference deconvolution. Theoretical and experimental results show that this approach leads to significant sensitivity improvements for typical systems and experimental conditions. Further sensitivity improvements or, equivalently, an extension of the accessible distance range can be obtained by matrix deuteration or digital long-pass filtering of the time-domain data. Advantages and limitations of the new variable-time experiment are discussed by comparing it to the established analogous constant-time experiment for measurements of end-to-end distances of 5 and 7.5 nm on rod-like shape-persistent biradicals and for the measurement of a broadly distributed transmembrane distance in a doubly spin-labeled mutant of plant light harvesting complex II. (C) 2004 Elsevier Inc. All rights reserved.