Korosec Chapin S, Jindal Lavisha, Schneider Mathew, Calderon de la Barca Ignacio, Zuckermann Martin J, Forde Nancy R, Emberly Eldon
Department of Physics, Simon Fraser University, 8888 University Drive, Burnaby, British Columbia V5A 1S6, Canada.
Soft Matter. 2021 Feb 19;17(6):1468-1479. doi: 10.1039/d0sm01811b.
Nature has evolved many mechanisms for achieving directed motion on the subcellular level. The burnt-bridges ratchet (BBR) is one mechanism used to achieve superdiffusive molecular motion over long distances through the successive cleavage of surface-bound energy-rich substrate sites. This mechanism has been associated with both nanoscale and microscale movement, with the latter accomplished through polyvalent interactions between a large hub (e.g. influenza virus) and substrate (e.g. cell surface receptors). Experimental successes in achieving superdiffusive motion by synthetic polyvalent BBRs have raised questions about the dynamics of their motility, including whether rolling or translation is better able to direct motion of microscale spherical hubs. Here we simulate the three-dimensional dynamics of a polyvalent sphere moving on and cleaving an elastic substrate. We find that substrate stiffness plays an important role in controlling both the motor's mode of motility and its directional persistence. As we tune lateral substrate stiffness from soft to stiff we find there exists an intermediate value that optimizes rolling behaviour. We also find that there is an optimal substrate stiffness for maximizing persistence length, while stiffness does not influence as strongly the superdiffusive dynamics of the particle. Lastly, we examine the effect of substrate density, and show that softer landscapes are better able to buffer against decreases in substrate occupancy, with the spherical motor maintaining superdiffusive motion more on softer landscapes than on stiff landscapes as occupancy drops. Our results highlight the importance of surface in controlling the motion of polyvalent BBRs.
自然界已经进化出许多机制来实现亚细胞水平上的定向运动。烧桥棘轮（BBR）是一种用于通过连续切割表面结合的富含能量的底物位点来实现长距离超扩散分子运动的机制。这种机制与纳米级和微米级运动都有关联，后者是通过大的中心体（如流感病毒）与底物（如细胞表面受体）之间的多价相互作用来完成的。通过合成多价BBR实现超扩散运动的实验成功引发了关于其运动动力学的问题，包括滚动或平移是否更能引导微米级球形中心体的运动。在这里，我们模拟了一个多价球体在弹性底物上移动并切割底物的三维动力学。我们发现底物刚度在控制马达的运动模式及其方向持续性方面起着重要作用。当我们将横向底物刚度从软调至硬时，我们发现存在一个中间值可优化滚动行为。我们还发现存在一个最佳底物刚度以最大化持续长度，而刚度对粒子的超扩散动力学的影响没有那么强烈。最后，我们研究了底物密度的影响，并表明较软的环境更能缓冲底物占有率的下降，随着占有率下降，球形马达在较软环境中比在硬环境中更能保持超扩散运动。我们的结果突出了表面在控制多价BBR运动方面的重要性。
