肌动蛋白纤维束的收缩：圣捷尔吉事件后50年
Contraction of a Bundle of Actin Filaments: 50 years after Szent-Gyorgyi
摘要：
生物系统是理论物理学家、实验学家或模拟学家最具挑战性的课题之一。物理学原理应该是数十亿年来生命系统进化的限制和指导方针。一个通常旨在澄清什么物理原理，可能是新的，是背后的生物学现象的兴趣，并在了解他们如何在整个生物世界的工作。在本演讲中，我们描述了这种努力的一个例子。自20世纪40年代Szent-Gyorgyi等人发现“超沉淀”以来，肌动蛋白纤维在肌动蛋白激活的ATP水解反应中如何发生收缩一直是一个谜。目前普遍认为，在收缩过程中，双头肌球蛋白介导了两条肌动蛋白丝的相对滑动，而这两条肌动蛋白丝的极性方向不是平行的，而是反平行的。但这一事实并不能完全解释缩短的原因。我们提出了一个动力学模型，在数值模拟，表现出缩短的一束肌动蛋白丝最初dirterted随机在空间中沿一条线和极性方向。在缩短的过程中，沿着纤维束出现了几个肌动蛋白簇。该模型还显示了后期肌动蛋白丝根据其极性的排序。这些发现与Takiguchi最近的实验一致。
英文摘要：
Biological systems are among the most challenging subjects for theoretical physicists, as well as experimentalists or simulationists. Physical principles should have been both constraints and guide-lines for the evolution of living systems over billions of years. One generally aims at clarifying what physical principles, possibly new ones, are behind the phenomena of biological interest and at understanding how they work within the entire biological world. In the present talk we describe an example of such an effort. Since the discovery of `superprecipitation' by Szent-Gyorgyi's group in 1940's, it has been a long puzzle how an assemblage of actin filaments with random orientation can contract in the presence of the two-headed myosin molecules undergoing actin-activated ATP-hydrolysis reaction. It is widely accepted that during the contraction the two-headed myosin mediates the relative sliding of two actin filaments whose polarity directions are not parallel but rather anti-parallel. But this fact solely does not account for the shortening. We propose a dynamical model which, upon numerical simulation, exhibits the shortening of an bundle of the actin filaments which are initially dirstributed randomly both in space along a line and in polarity direction. In the course of shortening several clusters of actins appears along the bundle. The model also shows the sorting of the actin filaments according to their polarity in the late stage. These findings are in accordance with the recent experiment by Takiguchi.
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