Institute for Integrative Biology of the Cell (I2BC), Department of Biochemistry, Biophysics and Structural Biology, Université Paris-Saclay, CEA, CNRS UMR 9198, Gif-sur-Yvette, F-91191, France.
Phys Chem Chem Phys. 2015 Sep 28;17(36):23368-77. doi: 10.1039/c5cp03487f. Epub 2015 Aug 19.
Pulse electron-electron double resonance (PELDOR) is a versatile technique for probing the structures and functions of complex biological systems. Despite the recent interest in high-spin metal-ions for high field/frequency applications, PELDOR measurements of Mn(ii) remain relatively underexplored. Here we present Mn(ii)-Mn(ii) PELDOR distance measurements at 94 GHz on polyproline II (PPII) helices doubly spin-labeled with Mn(ii)DOTA, which are distinguished by their small zero-field interaction. The measured Mn-Mn distances and distribution profiles were in good agreement with the expected values from molecular models. Additional features in the frequency-domain spectra became apparent at certain combinations of detect and pump frequencies. Spin-Hamiltonian calculations showed that they likely arose from contributions from the pseudo-secular component of the dipolar interaction that were found to be non-negligible for Mn(ii)DOTA. However, the influence of the pseudo-secular component on the distance distribution profiles apparently was limited. The results show the potential of Mn(ii)DOTA spin labels for high-field PELDOR distance measurements in proteins and other biological systems.
脉泽电子-电子双共振（PELDOR）是一种用于探测复杂生物系统结构和功能的多功能技术。尽管最近对高自旋金属离子在高场/高频应用中的应用产生了兴趣，但 Mn(ii) 的 PELDOR 测量仍然相对较少。在这里，我们在 94GHz 下对聚脯氨酸 II (PPII) 螺旋进行了 Mn(ii)-Mn(ii) PELDOR 距离测量，这些螺旋用 Mn(ii)DOTA 双重自旋标记，其特点是零场相互作用小。测量的 Mn-Mn 距离和分布谱与分子模型的预期值吻合良好。在探测和泵浦频率的某些组合下，频域谱中出现了附加特征。自旋哈密顿计算表明，它们可能来自偶极相互作用的伪周期分量的贡献，对于 Mn(ii)DOTA，发现该贡献不可忽略。然而，伪周期分量对距离分布谱的影响显然是有限的。结果表明，Mn(ii)DOTA 自旋标记在蛋白质和其他生物系统中的高场 PELDOR 距离测量中具有潜力。
