Centre for Research in Nanotechnology and Sciences, Indian Institute of Technology Bombay, Mumbai, India.
Department of Biosciences and Bioengineering, Indian Institute of Technology Bombay, Mumbai, India.
Sci Rep. 2017 Apr 4;7:45747. doi: 10.1038/srep45747.
Characterising complex kinetics of non-equilibrium self-assembly of bio-filaments is of general interest. Dynamic instability in microtubules, consisting of successive catastrophes and rescues, is observed to occur as a result of the non-equilibrium conversion of GTP-tubulin to GDP-tubulin. We study this phenomenon using a model for microtubule kinetics with GTP/GDP state-dependent polymerisation, depolymerisation and hydrolysis of subunits. Our results reveal a sharp switch-like transition in the mean velocity of the filaments, from a growth phase to a shrinkage phase, with an associated co-existence of the two phases. This transition is reminiscent of the discontinuous phase transition across the liquid-gas boundary. We probe the extent of discontinuity in the transition quantitatively using characteristic signatures such as bimodality in velocity distribution, variance and Binder cumulant, and also hysteresis behaviour of the system. We further investigate ageing behaviour in catastrophes of the filament, and find that the multi-step nature of catastrophes is intensified in the vicinity of the switching transition. This assumes importance in the context of Microtubule Associated Proteins which have the potential of altering kinetic parameter values.
描述非平衡生物纤维自组装的复杂动力学是普遍关注的问题。微管的不稳定性由 GTP-微管蛋白向 GDP-微管蛋白的非平衡转化引起，其表现为连续的灾难和救援。我们使用一种具有 GTP/GDP 状态依赖性聚合、解聚和亚基水解的微管动力学模型来研究这种现象。我们的结果揭示了纤维平均速度的急剧开关式转变，从生长阶段到收缩阶段，同时存在两种阶段的共存。这种转变让人联想到跨越液-气边界的不连续相变。我们使用速度分布的双峰性、方差和 Binder 累积量等特征标志以及系统的滞后行为，定量探测转变中的不连续性程度。我们进一步研究了纤维灾难中的老化行为，并发现灾难的多步性质在转换过渡附近加剧。这在微管相关蛋白的背景下具有重要意义，因为微管相关蛋白有可能改变动力学参数值。
