单分子拉伸实验中生物分子无序性的证据
Evidence of disorder in biological molecules from single molecule pulling experiments
摘要：
生物分子中的异质性，导致分子间动力学和功能的变化，是一个新兴的主题。为了阐明在单分子水平上的非均质行为的后果，我们提出了一个完全可解的模型，其中由于机械力的展开速率参数依赖于一个辅助变量，代表熵势垒所产生的内部动力学的波动。当波动率，动力学紊乱的措施，是可比的或小于力引起的解约束率，我们表明，有两个实验观察到的后果：在恒定的力的非指数生存概率，和重尾破裂力分布在恒定的加载速率。通过将我们的分析表达式与蛋白质和DNA单分子拉伸实验的数据拟合，我们量化了无序的程度。我们表明，只有通过分析数据在很大范围内的力量和加载速率可以定量评估的作用，由于内部动力学的混乱。
英文摘要：
Heterogeneity in biological molecules, resulting in molecule-to-molecule variations in their dynamics and function, is an emerging theme. To elucidate the consequences of heterogeneous behavior at the single molecule level, we propose an exactly solvable model in which the unfolding rate due to mechanical force depends parametrically on an auxiliary variable representing an entropy barrier arising from fluctuations in internal dynamics. When the rate of fluctuations, a measure of dynamical disorder, is comparable to or smaller than the rate of force-induced unbinding, we show that there are two experimentally observable consequences: non-exponential survival probability at constant force, and a heavy-tailed rupture force distribution at constant loading rate. By fitting our analytical expressions to data from single molecule pulling experiments on proteins and DNA, we quantify the extent of disorder. We show that only by analyzing data over a wide range of forces and loading rates can the role of disorder due to internal dynamics be quantitatively assessed.
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