Fisher M E, Kolomeisky A B
Institute for Physical Science and Technology, University of Maryland, College Park, MD 20742, USA.
Proc Natl Acad Sci U S A. 1999 Jun 8;96(12):6597-602. doi: 10.1073/pnas.96.12.6597.
The stochastic driving force exerted by a single molecular motor (e. g., a kinesin, or myosin) moving on a periodic molecular track (microtubule, actin filament, etc.) is discussed from a general viewpoint open to experimental test. An elementary "barometric" relation for the driving force is introduced that (i) applies to a range of kinetic and stochastic models, (ii) is consistent with more elaborate expressions entailing explicit representations of externally applied loads, and (iii) sufficiently close to thermal equlibrium, satisfies an Einstein-type relation in terms of the velocity and diffusion coefficient of the (load-free) motor. Even in the simplest two-state models, the velocity-vs.-load plots exhibit a variety of contrasting shapes (including nonmonotonic behavior). Previously suggested bounds on the driving force are shown to be inapplicable in general by analyzing discrete jump models with waiting time distributions.
从一个易于实验验证的通用视角出发，讨论了单个分子马达（如驱动蛋白或肌球蛋白）在周期性分子轨道（微管、肌动蛋白丝等）上移动时施加的随机驱动力。引入了一个关于驱动力的基本“气压”关系，该关系：（i）适用于一系列动力学和随机模型；（ii）与包含外部施加负载显式表示的更精细表达式一致；（iii）在足够接近热平衡的情况下，根据（无负载）马达的速度和扩散系数满足爱因斯坦型关系。即使在最简单的两态模型中，速度与负载的关系图也呈现出各种不同的形状（包括非单调行为）。通过分析具有等待时间分布的离散跳跃模型，表明先前提出的驱动力界限通常并不适用。
