Korea Institute for Advanced Study, Seoul 130-722, Korea.
Institute for Physical Science and Technology, University of Maryland, College Park, Maryland 20742, USA.
Phys Rev Lett. 2014 Apr 4;112(13):138101. doi: 10.1103/PhysRevLett.112.138101. Epub 2014 Mar 31.
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: nonexponential 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.
生物分子的异质性导致其动力学和功能在分子间发生变化，这是一个新兴的主题。为了阐明单分子水平上异质行为的后果，我们提出了一个完全可解的模型，其中由于机械力导致的展开速率与一个辅助变量相关，该辅助变量代表由内部动力学波动引起的熵垒。当波动的速率（一种衡量动态无序的度量）与力诱导解结合的速率相当或更小，我们表明存在两个可实验观察到的后果：在恒定力下的非指数生存概率，以及在恒定加载速率下的重尾断裂力分布。通过将我们的分析表达式拟合到蛋白质和 DNA 的单分子拉伸实验数据，我们量化了无序的程度。我们表明，只有通过在广泛的力和加载速率范围内分析数据，才能定量评估内部动力学引起的无序的作用。
