Twist-stretch coupling and phase transition during DNA supercoiling.
Twist-stretch coupling and phase transition during DNA supercoiling.
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DNA 超螺旋过程中的扭转-拉伸耦合和相变。
DOI：
10.1039/b901646e
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发表时间：
2009
期刊：
影响因子：
--
通讯作者：
Wang,MichelleD
中科院分区：
文献类型：
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作者：
Sheinin,MaximY;Wang,MichelleD
当单个 DNA 分子在恒定张力下呈正超螺旋时，由于负扭曲-拉伸耦合，其延伸最初会增加。随后达到最大延伸量先前被认为表明从 B-DNA 到 scP-DNA 相变的开始。在这里，我们表明，延伸最大值实际上与相变的开始并不相符。使用角光阱对扭矩平台的直接观察证明了这种转变。相反，我们发现延伸曲线的形状可以用结合 DNA 扭曲-拉伸耦合和弯曲波动的理论来很好地解释。该理论还提供了一种更准确的方法来确定扭转拉伸耦合模量的值，在以前的没有考虑弯曲波动的研究中，该模量可能被低估。我们的研究证明了扭矩检测在正确识别相变中的重要性以及扭转-拉伸耦合和弯曲波动对 DNA 延伸的贡献。
As a single DNA molecule is positively supercoiled under constant tension, its extension initially increases due to a negative twist–stretch coupling. The subsequent attainment of an extension maximum has previously been assumed to be indicative of the onset of a phase transition from B- to scP-DNA. Here we show that an extension maximum in fact does not coincide with the onset of a phase transition. This transition is evidenced by a direct observation of a torque plateau using an angular optical trap. Instead we find that the shape of the extension curve can be well explained with a theory that incorporates both DNA twist–stretch coupling and bending fluctuations. This theory also provides a more accurate method of determining the value of the twist–stretch coupling modulus, which has possibly been underestimated in previous studies that did not take into consideration the bending fluctuations. Our study demonstrates the importance of torque detection in the correct identification of phase transitions as well as the contribution of the twist–stretch coupling and bending fluctuations to DNA extension.