Elastic Strain Waves in Single Muscle Fibers

肌肉收缩是由肌凝蛋白分子部分附着在肌动蛋白丝上的构象变化所驱动的。这种形状的变化导致这两种肌肉蛋白质之间的滑动运动，从而缩短了整个肌肉。试图理解这一系统的动力学依赖于两种方法：(1)实验，采用快速机械瞬态应用于激活的肌肉；(2)质量作用模型，将这些蛋白质视为独立的化学物质。我们的研究用理论和实验相结合的方法重新审视了这两种方法。从理论的角度来看，我们将证明应用于单个肌肉细胞制备的快速机械扰动会导致内部应变的传播波，并且这些波可能解释了被错误地归因于肌球蛋白动力学的行为。使用最近的实验方法，采用高速激光衍射，我们显示这样的波发生，我们用这样的数据来证实我们的理论预测。我们还将开发一种新的理论方法来模拟相互作用蛋白质的动力学。在这种新方法中，我们放松了每个肌球蛋白分子独立作用的假设。相反，我们认为每个分子的动力学可以表示为振荡器，其行为取决于其邻近肌凝蛋白的动力学。这种耦合振荡系统可以产生与每个分子的动力学大不相同的分子集合的动力学。这两种方法挑战了传统观点，即肌肉是一个缓慢的、独立的分子系统，其动力学可以通过使用快速机械扰动的实验提取

Muscle contraction is driven by conformational changes associated with portions of myosin molecules when they are attached to actin filaments. This shape change results in a sliding motion between these two muscle proteins and thus, shortening of the entire muscle. Attempts to understand the dymamics of this system have relied on two approaches: (1) experiments that employ rapid mechanical transients applied to activated muscle and (2) mass action models that treat these proteins as independent chemical species. Our research re-examines these two approaches with a combination of theoretical and experimental approaches. From a theoretical standpoint, we will show that rapid mechanical perturbations applied to single muscle cell preparations lead to propagating waves of internal strain and that these waves may account for the behaviors that have been incorrectly attributed to mysosin kinetics. Using recent experimental methods that employ high - speed laser diffractometry, we show such waves occur and we use such data to corroborate our theoretical predictions. We will also develop a new theoretical approach for modelling thedynamics of interacting proteins. In this new approach, we relax the assumption that each myosin molecule acts independently. Instead, we argue that the kinetics of each molecule can be represented as an oscillator whose behavior depends on the kinetics of its neighboring myosins. This system of coupled oscillators can yield kinetics of an ensemble of molecules that is vastly different from the kinetics of each individual. These two approaches challenge the classic views of muscle as a system of slow, independent molecules whose kinetics can be extracted from experiments employing rapid mechanical perturbations.//