Dpto de Física de la Materia Condensada and BIFI, Universidad de Zaragoza, 50009 Zaragoza, Spain.
Phys Biol. 2010 Nov 22;7(4):046009. doi: 10.1088/1478-3975/7/4/046009.
We analyze theoretically the effects of excluded-volume interactions between motors on the dynamics of a cargo driven by multiple motors. The model considered shares much in common with others recently proposed in the literature, with the addition of direct interaction between motors and motor back steps. The cargo is assumed to follow a continuum Langevin dynamics, while individual motors evolve following a Monte Carlo algorithm based on experimentally accessible probabilities for discrete forward and backward jumps, and attachment and detachment rates. The links between cargo and motors are considered as nonlinear springs. By means of numerical simulations we compute the relevant quantities characterizing the dynamical properties of the system, and we compare the results to those for noninteracting motors. We find that interactions lead to quite relevant changes in the force-velocity relation for cargo, with a considerable reduction of the stall force, and also cause a notable decrease of the run length. These effects are mainly due to traffic-like phenomena in the microtubule. The consideration of several parallel tracks for motors reduces such effects. However, we find that for realistic values of the number of motors and the number of tracks, the influence of interactions on the global parameters of transport of cargo are far from being negligible. Our studies also provide an analysis of the relevance of motor back steps on the modeling, and of the influence of different assumptions for the detachment rates. In particular, we discuss these two aspects in connection with the possibility of observing processive back motion of cargo at large load forces.
我们从理论上分析了马达之间的排斥体积相互作用对由多个马达驱动的货物动力学的影响。所考虑的模型与文献中最近提出的其他模型有很多共同之处，除了马达和马达后退步之间的直接相互作用。假设货物遵循连续朗之万动力学，而单个马达则根据实验上可获得的离散前向和后向跳跃、附着和脱离速率的概率，遵循基于蒙特卡罗算法进行演化。货物和马达之间的连接被视为非线性弹簧。通过数值模拟，我们计算了描述系统动力学特性的相关量，并将结果与非相互作用马达的结果进行了比较。我们发现相互作用导致货物的力-速度关系发生相当大的变化，停动力显著降低，运行长度也明显缩短。这些效应主要是由于微管中的交通样现象引起的。考虑几个平行的马达轨道可以减少这些影响。然而，我们发现对于马达数量和轨道数量的实际值，相互作用对货物整体运输参数的影响远非微不足道。我们的研究还提供了对马达后退步在建模中的重要性的分析，以及对不同脱离速率假设的影响的分析。特别是，我们讨论了这两个方面与在大负载力下观察到货物的连续后退运动的可能性有关。
