S-DNA的微观意义
Microscopic implications of S-DNA
摘要：
最近的实验[J. van Mameren et al. PNAS 106，18231（2009）]提供了过度拉伸DNA的详细空间图像，显示在某些条件下双螺旋的两条链在约65 pN处分离。有人提出，这一观察排除了存在一种伸长的杂交形式的DNA（“S-DNA”）。在这里，我们认为，S-DNA的图片是一致的观察在过度拉伸的剥离。我们证明，假设S-DNA的存在并不意味着DNA过度拉伸组成的分子从B-到S-形式的完全或接近完全的转换。相反，这种假设通常意味着杂交和未杂交形式的DNA的更复杂的动态共存。我们认为，这种共存可以合理化最近的几个实验观察。
英文摘要：
Recent experiments [J. van Mameren et al. PNAS 106, 18231 (2009)] provide a detailed spatial picture of overstretched DNA, showing that under certain conditions the two strands of the double helix separate at about 65 pN. It was proposed that this observation rules out the existence of an elongated, hybridized form of DNA ('S-DNA'). Here we argue that the S-DNA picture is consistent with the observation of unpeeling during overstretching. We demonstrate that assuming the existence of S-DNA does not imply DNA overstretching to consist of the complete or near-complete conversion of the molecule from B- to S-form. Instead, this assumption implies in general a more complex dynamic coexistence of hybridized and unhybridized forms of DNA. We argue that such coexistence can rationalize several recent experimental observations.
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