Chen Yi-der, Yan Bo, Rubin Robert J
Mathematical Research Branch, National Institute of Diabetes, Digestive and Kidney Diseases, National Institutes of Health, BSA Building Suite 350, 9000 Rockville Pike, Bethesda, MD 20892-2690, USA.
Biophys J. 2002 Nov;83(5):2360-9. doi: 10.1016/S0006-3495(02)75250-8.
The motility assay of K. Visscher, M. J. Schnitzer, and S. M. Block (Nature, 400:184-189, 1999) in which the movement of a bead powered by a single kinesin motor can be measured is a very useful tool in characterizing the force-dependent steps of the mechanochemical cycle of kinesin motors, because in this assay the external force applied to the bead can be controlled (clamped) arbitrarily. However, because the bead is elastically attached to the motor and the response of the clamp is not fast enough to compensate the Brownian motion of the bead, interpretation or analysis of the data obtained from the assay is not trivial. In a recent paper (Y. Chen and B. Yan, Biophys. Chem. 91:79-91, 2001), we showed how to evaluate the mean velocity of the bead and the motor in the motility assay for a given mechanochemical cycle. In this paper we extend the study to the evaluation of the fluctuation or the randomness of the velocity using a Monte Carlo simulation method. Similar to the mean, we found that the randomness of the velocity of the motor is also influenced by the parameters that affect the dynamic behavior of the bead, such as the viscosity of the medium, the size of the bead, the stiffness of the elastic element connecting the bead and the motor, etc. The method presented in this paper should be useful in modeling the kinetic mechanism of any processive motor (such as conventional kinesin and myosin V) based on measured force-clamp motility data.
K. 维斯彻、M. J. 施尼策和S. M. 布洛克于1999年发表在《自然》杂志上的运动性检测方法（400:184 - 189），可用于测量由单个驱动蛋白马达驱动的珠子的运动，是表征驱动蛋白马达机械化学循环中力依赖步骤的非常有用的工具，因为在该检测中施加于珠子的外力可被任意控制（钳制）。然而，由于珠子通过弹性连接到马达，且钳制的响应速度不够快，无法补偿珠子的布朗运动，因此对该检测获得的数据进行解释或分析并非易事。在最近一篇论文（Y. 陈和B. 严，《生物物理化学》91:79 - 91，2001）中，我们展示了如何在给定的机械化学循环的运动性检测中评估珠子和马达的平均速度。在本文中，我们使用蒙特卡罗模拟方法将研究扩展到速度波动或随机性的评估。与平均值类似，我们发现马达速度的随机性也受到影响珠子动态行为的参数的影响，例如介质的粘度、珠子的大小、连接珠子和马达的弹性元件的刚度等。本文提出的方法对于基于测量的力钳制运动性数据对任何进行性马达（如传统驱动蛋白和肌球蛋白V）的动力学机制进行建模应该是有用的。
