Fedin Matvey V, Shevelev Georgiy Yu, Pyshnyi Dmitrii V, Tormyshev Victor M, Jeschke Gunnar, Yulikov Maxim, Bagryanskaya Elena G
International Tomography Center SB RAS, Novosibirsk, 630090, Russia.
Novosibirsk State University, Novosibirsk, 630090, Russia and Institute of Chemical Biology and Fundamental Medicine SB RAS, Novosibirsk, 630090, Russia.
Phys Chem Chem Phys. 2016 Oct 26;18(42):29549-29554. doi: 10.1039/c6cp05904j.
Spin labels selectively attached to biomolecules allow high-accuracy nanoscale distance measurements using pulsed electron paramagnetic resonance (EPR), in many cases providing the only access to the structure of complex biosystems. Triarylmethyl (TAM) radicals have recently emerged as a new class of spin labels expanding the applicability of the method to physiological temperatures. Along with other factors, the accuracy of the obtained distances crucially relies on the understanding of interactions between biomolecules and spin labels. In this work, we consider such crucial interactions and their impact on pulsed EPR distance measurements in TAM-labeled DNAs. Using orientation-selective high-frequency (94 GHz) double electron-electron resonance (DEER) we demonstrate strong specific interactions between DNA termini and TAM labels, leading to a significant restriction of their conformational mobility. An understanding of such interactions guides the way to select optimum TAM-labeling strategies, thus refining nanoscale EPR distance measurements in nucleic acids and their complexes under physiological conditions.
选择性附着于生物分子的自旋标记物，能够利用脉冲电子顺磁共振（EPR）进行高精度的纳米级距离测量，在许多情况下，这是获取复杂生物系统结构的唯一途径。三芳基甲基（TAM）自由基最近作为一类新型自旋标记物出现，将该方法的适用范围扩展到了生理温度。与其他因素一样，所获距离的准确性在很大程度上依赖于对生物分子与自旋标记物之间相互作用的理解。在这项工作中，我们考虑了此类关键相互作用及其对TAM标记的DNA中脉冲EPR距离测量的影响。利用取向选择性高频（94 GHz）双电子 - 电子共振（DEER），我们证明了DNA末端与TAM标记物之间存在强烈的特异性相互作用，这导致它们的构象流动性受到显著限制。对这种相互作用的理解为选择最佳的TAM标记策略指明了方向，从而在生理条件下优化核酸及其复合物中的纳米级EPR距离测量。
