Keller Katharina, Zalibera Michal, Qi Mian, Koch Vanessa, Wegner Julia, Hintz Henrik, Godt Adelheid, Jeschke Gunnar, Savitsky Anton, Yulikov Maxim
Laboratory of Physical Chemistry, Department of Chemistry and Applied Bioscience, ETH Zurich, Vladimir Prelog Weg 2, 8093 Zurich, Switzerland.
Max Planck Institut for Chemical Energy Conversion, Stiftstrasse 34-36, D-45470 Mülheim an der Ruhr, Germany.
Phys Chem Chem Phys. 2016 Sep 14;18(36):25120-25135. doi: 10.1039/c6cp04884f.
The four Mn(ii) complexes Mn-DOTA, Mn-TAHA, Mn-PyMTA, and Mn-NO3Py were characterized by electron paramagnetic resonance (EPR), electron-nuclear double resonance (ENDOR), and relaxation measurements, to predict their relative performance in the EPR pulse dipolar spectroscopy (PDS) experiments. High spin density localization on the metal ions was proven by ENDOR on H, D, N, and Mn nuclei. The transverse relaxation of the Mn(ii) complexes appears to be slow enough for PDS-based spin-spin distance determination. Rather advantageous ratios of T/T were measured allowing for good relaxation induced dipolar modulation enhancement (RIDME) performance and, in general, fast shot repetitions in any PDS experiment. Relaxation properties of the Mn(ii) complexes correlate with the strengths of their zero field splitting (ZFS). Further, a comparison of Mn(ii)-DOTA and Gd(iii)-DOTA based spin labels is presented. The RIDME technique to measure nanometer-range Mn(ii)-Mn(ii) distances in biomolecules is discussed as an alternative to the well-known DEER technique that often appears challenging in cases of metal-metal distance measurements. The use of a modified kernel function that includes dipolar harmonic overtones allows model-free computation of the Mn(ii)-Mn(ii) distance distributions. Mn(ii)-Mn(ii) distances are computed from RIDME data of Mn-rulers consisting of two Mn-PyMTA complexes connected by a rodlike spacer of defined length. Level crossing effects seem to have only a weak influence on the distance distributions computed from this set of Mn(ii)-Mn(ii) RIDME data.
通过电子顺磁共振（EPR）、电子 - 核双共振（ENDOR）和弛豫测量对四种锰（II）配合物Mn - DOTA、Mn - TAHA、Mn - PyMTA和Mn - NO3Py进行了表征，以预测它们在EPR脉冲偶极光谱（PDS）实验中的相对性能。通过对H、D、N和Mn核的ENDOR证明了金属离子上的高自旋密度定位。锰（II）配合物的横向弛豫似乎足够慢，可用于基于PDS的自旋 - 自旋距离测定。测量到了相当有利的T/T比，允许良好的弛豫诱导偶极调制增强（RIDME）性能，并且通常在任何PDS实验中都能实现快速的脉冲重复。锰（II）配合物的弛豫性质与其零场分裂（ZFS）的强度相关。此外，还对基于锰（II） - DOTA和钆（III） - DOTA的自旋标记进行了比较。讨论了用于测量生物分子中纳米级锰（II） - 锰（II）距离的RIDME技术，作为在金属 - 金属距离测量中常常具有挑战性的著名双电子电子共振（DEER）技术的替代方法。使用包含偶极谐波泛音的修正核函数可实现锰（II） - 锰（II）距离分布的无模型计算。锰（II） - 锰（II）距离是根据由两个通过确定长度的棒状间隔物连接的Mn - PyMTA配合物组成的锰尺的RIDME数据计算得出的。能级交叉效应似乎对从这组锰（II） - 锰（II）RIDME数据计算出的距离分布只有微弱影响。
