Rudolf Peierls Centre for Theoretical Physics, University of Oxford, 1 Keble Road, Oxford OX1 3NP, United Kingdom.
Phys Rev Lett. 2012 Nov 30;109(22):228101. doi: 10.1103/PhysRevLett.109.228101.
Although mechanical properties of DNA are well characterized at the kilobase-pair range, a number of recent experiments have suggested that DNA is more flexible at shorter length scales, which correspond to the regime that is crucial for cellular processes such as DNA packaging and gene regulation. Here, we perform a systematic study of the effective elastic properties of DNA at different length scales by probing the conformation and fluctuations of DNA from the single base-pair level up to four helical turns, using trajectories from atomistic simulation. We find evidence that supports cooperative softening of the stretch modulus and identify the essential modes that give rise to this effect. The bend correlation exhibits modulations that reflect the helical periodicity, while it yields a reasonable value for the effective persistence length, and the twist modulus undergoes a smooth crossover--from a relatively smaller value at the single base-pair level to the bulk value--over half a DNA turn.
尽管在千碱基对范围内已经很好地描述了 DNA 的力学性质，但最近的一些实验表明，在更短的长度尺度上 DNA 更具柔韧性，这对应于对细胞过程（如 DNA 包装和基因调控）至关重要的范围。在这里，我们通过从单个碱基对水平到四个螺旋圈的原子模拟轨迹，系统地研究了 DNA 在不同长度尺度上的有效弹性性质。我们发现了支持拉伸模量协同软化的证据，并确定了产生这种效应的基本模式。弯曲相关性表现出反映螺旋周期性的调制，同时为有效持久长度提供了合理的值，而扭转模量则经历了平滑的转变——从单个碱基对水平的相对较小值转变为整体值——超过半个 DNA 转。
