On the origin of the unusual behavior in the stretching of single-stranded DNA.
On the origin of the unusual behavior in the stretching of single-stranded DNA.
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DOI：
10.1063/1.4729371
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发表时间：
2012-05
期刊：
影响因子：
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通讯作者：
N. M. Toan;D. Thirumalai
中科院分区：
文献类型：
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作者：
N. M. Toan;D. Thirumalai
力-延伸曲线（FEC），其量化受到机械力（f）的各种生物分子的响应，通常使用蠕虫状链（WLC）或自由连接链（FJC）模型定量拟合。这些模型预测，在小的f和大的力标度下，由轮廓长度归一化的链延伸x线性增加，为x ~（1 - f（-α）），其中对于WLC α = 0.5，对于FJC α = 1。相比之下，单链DNA（ssDNA）的实验表明，在一定的f和离子浓度范围内，x的尺度为x ~ ln f，这不能用WLC或FJC模型来解释。使用理论和模拟，我们表明，这种不寻常的行为在FEC中的ssDNA是由于序列独立的双链效应。我们表明，x ~ ln f的出现，因为在没有力的正切相关函数，量化链持久性，代数衰减的德拜长度的顺序上的长度尺度。我们的理论，这是最合适的单价盐，定量拟合的实验数据，并进一步预测，这样的制度是不可辨别的双链DNA。
Force-extension curves (FECs), which quantify the response of a variety of biomolecules subject to mechanical force (f), are often quantitatively fit using worm-like chain (WLC) or freely jointed chain (FJC) models. These models predict that the chain extension, x, normalized by the contour length increases linearly at small f and at high forces scale as x ~ (1 - f(-α)), where α = 0.5 for WLC and unity for FJC. In contrast, experiments on single-stranded DNA (ssDNA) show that over a range of f and ionic concentration, x scales as x ~ ln f, which cannot be explained using WLC or FJC models. Using theory and simulations we show that this unusual behavior in FEC in ssDNA is due to sequence-independent polyelectrolyte effects. We show that the x ~ ln f arises because in the absence of force the tangent correlation function, quantifying chain persistence, decays algebraically on length scales on the order of the Debye length. Our theory, which is most appropriate for monovalent salts, quantitatively fits the experimental data and further predicts that such a regime is not discernible in double-stranded DNA.