arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 1206.4475q-bio.BMcond-mat.softcond-mat.stat-mechphysics.bio-ph
收藏

通过力谱法测定的Na $^+$和Mg $^{2+}$与RNA的非特异性结合

Non-specific binding of Na$^+$ and Mg$^{2+}$ to RNA determined by force spectroscopy methods

C. V. Bizarro, A. Alemany, F. Ritort

摘要:

RNA双链体的稳定性强烈依赖于离子条件,并且在细胞内RNA暴露于单价和多价离子。尽管最近的进展,我们没有一般的方法来定量说明单价和多价离子对RNA稳定性的影响,和二级结构预测的热力学参数仅在1 M [Na $^+$ ]。在这里,通过机械展开和折叠的20 bp的RNA发夹使用光镊,我们研究了RNA的热力学和动力学在不同的单价和混合单价/镁$^{2+}$盐条件。我们测量的展开和折叠断裂力,并应用Kramers理论提取准确的信息发夹自由能景观在广泛的离子条件下的张力。我们获得了非特异性的修正的RNA发夹形成的自由能和测量的距离的过渡态的折叠状态的变化与力和离子强度。我们通过实验验证了紧束缚离子模型,并获得了ssRNA的持续长度值。最后,我们测试了近似规则,通过该规则,对于小分子构建体,在给定浓度下二价阳离子的非特异性结合亲和力等于在该浓度的100倍下的单价阳离子的非特异性结合亲和力。

英文摘要:

RNA duplex stability depends strongly on ionic conditions, and inside cells RNAs are exposed to both monovalent and multivalent ions. Despite recent advances, we do not have general methods to quantitatively account for the effects of monovalent and multivalent ions on RNA stability, and the thermodynamic parameters for secondary structure prediction have only been derived at 1M [Na$^+$]. Here, by mechanically unfolding and folding a 20 bp RNA hairpin using optical tweezers, we study the RNA thermodynamics and kinetics at different monovalent and mixed monovalent/Mg$^{2+}$ salt conditions. We measure the unfolding and folding rupture forces and apply Kramers theory to extract accurate information about the hairpin free energy landscape under tension at a wide range of ionic conditions. We obtain non-specific corrections for the free energy of formation of the RNA hairpin and measure how the distance of the transition state to the folded state changes with force and ionic strength. We experimentally validate the Tightly Bound Ion model and obtain values for the persistence length of ssRNA. Finally, we test the approximate rule by which the non-specific binding affinity of divalent cations at a given concentration is equivalent to that of monovalent cations taken at 100 fold that concentration for small molecular constructs.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

↑