Azarkh Mykhailo, Keller Katharina, Qi Mian, Godt Adelheid, Yulikov Maxim
Department of Chemistry, University of Konstanz, Universitätsstraße 10, 78457 Konstanz, Germany.
Laboratory of Physical Chemistry, Department of Chemistry and Applied Biosciences, ETH Zurich, Vladimir-Prelog-Weg 2, 8093 Zurich, Switzerland.
J Magn Reson. 2022 Jun;339:107217. doi: 10.1016/j.jmr.2022.107217. Epub 2022 Apr 9.
Relaxation-induced dipolar modulation enhancement (RIDME) is a pulse EPR technique that is particularly suitable to determine distances between paramagnetic centers with a broad EPR spectrum, e.g. metal-ion-based ones. As far as high-spin systems (S > ½) are concerned, the RIDME experiment provides not only the basic dipolar frequency but also its overtones, which complicates the determination of interspin distances. Here, we present and discuss in a step-by-step fashion an r.m.s.d.-based approach for the calibration of the overtone coefficients for a series of molecular rulers doubly labeled with Gd(III)-PyMTA tags. The constructed 2D total-penalty diagrams help revealing that there is no unique set of overtone coefficients but rather a certain pool, which can be used to extract distance distributions between high-spin paramagnetic centers, as determined from the RIDME experiment. This is of particular importance for comparing RIDME overtone calibration and distance distributions obtained in different labs.
弛豫诱导偶极调制增强（RIDME）是一种脉冲电子顺磁共振技术，特别适用于确定具有宽电子顺磁共振谱的顺磁中心之间的距离，例如基于金属离子的顺磁中心。就高自旋体系（S>1/2）而言，RIDME实验不仅提供基本的偶极频率，还提供其泛音，这使得自旋间距离的测定变得复杂。在这里，我们逐步介绍并讨论一种基于均方根偏差的方法，用于校准一系列用Gd(III)-PyMTA标签双标记的分子尺的泛音系数。构建的二维总惩罚图有助于揭示不存在唯一的一组泛音系数，而是有一个特定的集合，可用于从RIDME实验中提取高自旋顺磁中心之间的距离分布。这对于比较不同实验室获得的RIDME泛音校准和距离分布尤为重要。
