Opposing Effects of Multivalent Ions on the Flexibility of DNA and RNA.
Opposing Effects of Multivalent Ions on the Flexibility of DNA and RNA.
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DOI：
10.1103/physrevlett.117.028101
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发表时间：
2016-07-08
影响因子：
8.6
通讯作者：
Onufriev AV
中科院分区：
文献类型：
--
作者：
Drozdetski AV;Tolokh IS;Pollack L;Baker N;Onufriev AV
已知反离子（盐）浓度的增加会减少DNA的弯曲持续长度。在这里，我们使用原子分子动力学模拟来预测多价反离子对双链RNA具有相反的作用，使其弯曲刚度增加至少30%。这种反直觉的效应在各种三价和四价离子中都被观察到，并且对方法细节和RNA序列是稳健的。与DNA相反，多价反离子结合在RNA主槽内，导致分子沿着螺旋轴显著收缩——因此，与没有结合多价离子的弯曲相比，弯曲引起的进一步变形在能量上更加昂贵。因此，带电聚合物的机械性能与其离子气氛之间的关系可能比以前认为的更丰富。
Increasing concentration of counterions (salt) is known to reduce the bending persistence length of DNA. Here we use atomistic molecular dynamics simulations to predict that multivalent counterions have the opposite effect on double-stranded RNA, increasing its bending rigidity by at least 30%. This counter-intuitive effect is observed for various tri- and tetravalent ions alike, and is robust to methodological details and RNA sequence. In contrast to DNA, multivalent counterions bind inside the RNA major groove, causing significant contraction of the molecule along its helical axis — as a result, its further deformation due to bending becomes energetically more expensive compared to bending without bound multivalent ions. Thus, the relationship between mechanical properties of a charged polymer and its ionic atmosphere may be richer than previously thought.