Department of Physics and Key Laboratory of Artificial Micro & Nano-structures of Ministry of Education, School of Physics and Technology, Wuhan University, Wuhan 430072, China.
College of Life Sciences, the Institute for Advanced Studies, State Key Laboratory of Virology, Hubei Key Laboratory of Cell Homeostasis, Wuhan University, Wuhan 430072, China.
Phys Rev Lett. 2022 Mar 11;128(10):108103. doi: 10.1103/PhysRevLett.128.108103.
When stretched, both DNA and RNA duplexes change their twist angles through twist-stretch coupling. The coupling is negative for DNA but positive for RNA, which is not yet completely understood. Here, our magnetic tweezers experiments show that the coupling of RNA reverses from positive to negative by multivalent cations. Combining with the previously reported tension-induced negative-to-positive coupling reversal of DNA, we propose a unified mechanism of the couplings of both RNA and DNA based on molecular dynamics simulations. Two deformation pathways are competing when stretched: shrinking the radius causes positive couplings but widening the major groove causes negative couplings. For RNA whose major groove is clamped by multivalent cations and canonical DNA, their radii shrink when stretched, thus exhibiting positive couplings. For elongated DNA whose radius already shrinks to the minimum and canonical RNA, their major grooves are widened when stretched, thus exhibiting negative couplings.
拉伸时，DNA 和 RNA 双链都通过扭转拉伸耦合改变其扭转角。这种耦合对于 DNA 是负的，但对于 RNA 是正的，这一点尚未完全理解。在这里，我们的磁镊实验表明，通过多价阳离子，RNA 的耦合从正变为负。结合以前报道的张力诱导的 DNA 从负到正的耦合反转，我们基于分子动力学模拟提出了 RNA 和 DNA 耦合的统一机制。拉伸时存在两种竞争的变形途径：缩小半径会导致正耦合，但拓宽大沟会导致负耦合。对于其大沟被多价阳离子和规范 DNA 夹在中间的 RNA，拉伸时其半径缩小，因此表现出正耦合。对于拉长的 DNA，其半径已经缩小到最小，而规范的 RNA，拉伸时其大沟变宽，因此表现出负耦合。
