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首页> 外文期刊>Proceedings of the National Academy of Sciences of the United States of America >Stretched exponential decay and correlations in the catalytic activity of fluctuating single lipase molecules
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Stretched exponential decay and correlations in the catalytic activity of fluctuating single lipase molecules

机译：扩展的指数衰减和波动的单个脂肪酶分子的催化活性的相关性

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摘要

Single-molecule techniques offer a unique tool for studying the dynamical behavior of individual molecules and provide the possibility to construct distributions from individual events rather than from a signal stemming from an ensemble of molecules. In biological systems, known for their complexity, these techniques make it possible to gain insights into the detailed spectrum of molecular conformational changes and activities. Here, we report on the direct observation of a single lipase-catalyzed reaction for extended periods of time (hours), by using confocal fluorescence microscopy. When adding a profluorescent substrate, the monitored enzymatic activity appears as a trajectory of "on-state" and "off-state" events. The waiting time probability density function of the off state and the state-correlation function fit stretched exponentials, independent of the substrate concentration in a certain range. The data analysis unravels oscillations in the logarithmic derivative of the off-state waiting time probability density function and correlations between off-state events. These findings imply that the fluctuating enzyme model, which involves a spectrum of enzymatic conformations that interconvert on the time scale of the catalytic activity, best describes the observed enzymatic activity. Based on this model, values for the coupling and reaction rates are extracted.
机译：单分子技术为研究单个分子的动力学行为提供了一种独特的工具，并提供了从单个事件而不是从分子整体的信号构造分布的可能性。在以复杂性着称的生物系统中，这些技术可以深入了解分子构象变化和活性的详细光谱。在这里，我们报告使用共聚焦荧光显微镜观察单个脂肪酶催化的反应延长的时间（小时）。当添加前荧光底物时，所监测的酶活性表现为“开启状态”和“关闭状态”事件的轨迹。断开状态的等待时间概率密度函数和状态相关函数与拉伸指数拟合，而与衬底浓度在一定范围内无关。数据分析揭示了关闭状态等待时间概率密度函数的对数导数的振荡以及关闭状态事件之间的相关性。这些发现暗示波动的酶模型最好地描述了观察到的酶活性，该波动的酶模型涉及在催化活性的时间尺度上相互转化的一系列酶构象。基于该模型，提取耦合和反应速率的值。

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