标题： 纤维与障碍物相互作用对生长生物聚合物的力-速度关系的影响 显示英文标题

标题： The effect of the filament-obstacle interaction on the force-velocity relation of a growing biopolymer

摘要： 我们通过显式处理障碍物扩散以及亚基的随机添加和去除，研究了丝状物-障碍物相互作用对生长生物聚合物的力-速度关系的影响。 我们首先证明，亚基的结合和解离速率满足由丝状物-障碍物相互作用势确定的严格热力学关系。 结合和解离速率不仅取决于作用在障碍物上的平均力，还取决于纳米尺度上势的形状。 仅基于力来估计障碍物引起的结合速率降低，在作用在丝状物尖端的力存在波动时会高估停顿力。 然后我们使用热力学关系进行模拟和解析计算。 我们发现，与一般热力学关系的预期一致，"布朗-Ratchet"模型是生长速度的上限，并且对于纯排斥势，生长速度基本上等于布朗-Ratchet模型所预测的值。 对于深度约为5k_BT的浅势阱，这可能对应于短暂的丝状物-膜连接，零力下的速度是自由丝状物速度的一个显著部分。 在这种情况下，即使无量纲扩散系数很大，生长速度也可能强烈依赖于障碍物扩散系数。 速度的下降比布朗-Ratchet模型预测的更快，在某些情况下，当对抗力为1 pN时，下降幅度可达50倍。 对于深势阱，如可能由强丝状物-膜连接产生的势阱，结合和解离速率都会显著降低，从而减缓聚合过程。 这样的势阱可以在聚合过程中维持拉力，但前提是吸引力势阱有一个与单体尺寸相当或更大的"平台"。 显示英文摘要

摘要： We investigate the effect of filament-obstacle interactions on the force-velocity relation of growing biopolymers, via calculations explicitly treating obstacle diffusion and stochastic addition and subtraction of subunits. We first show that the subunit on- and off-rates satisfy a rigorous thermodynamic relationship determined by the filament-obstacle interaction potential. Both the on- and off-rates depend not only on the average force on the obstacle, but also on the shape of the potential on the nanometer length scale. Basing obstacle-induced reduction of the on-rate entirely on the force overestimates the stall force when there are fluctuations in the force exerted on a filament tip. We then perform simulations and analytic calculations using the thermodynamic relationship. We find, consistent with expectations from general thermodynamic relations, that the "Brownian-Ratchet" model is an upper bound to the growth velocity and that for purely repulsive potentials the growth velocity is essentially that predicted by the Brownian-Ratchet model. For shallow potential wells of depth ~ 5k_BT, which might correspond to transient filament-membrane attachments, the zero-force velocity is a substantial fraction of the free-filament velocity. In this case, the growth velocity can depend strongly on the obstacle diffusion coefficient even when the dimensionless diffusion coefficient is large. The velocity also drops more rapidly than predicted by the Brownian-ratchet model, in some cases by as much as a factor of 50 at an opposing force of 1 pN. For deep potential wells, as might result from strong filament-membrane links, both the on- and off-rates are reduced significantly, slowing polymerization. Such potentials can sustain pulling forces while polymerizing, but only if the attractive well has a "shelf" comparable to or greater than the monomer size.