title: Signatures of a macroscopic switching transition for a dynamic microtubule.
abstract: 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.
authors.affiliation: Centre for Research in Nanotechnology and Sciences, Indian Institute of Technology Bombay, Mumbai, India.
authors.forename: J S
authors.initials: JS
authors.lastname: Aparna
authors.affiliation: Department of Biosciences and Bioengineering, Indian Institute of Technology Bombay, Mumbai, India.
authors.forename: Ranjith
authors.initials: R
authors.lastname: Padinhateeri
authors.affiliation: Department of Physics, Indian Institute of Technology Bombay, Mumbai, India.
authors.forename: Dibyendu
authors.initials: D
authors.lastname: Das
mesh_terms: D006153:Guanosine Diphosphate / Q000378:metabolism; D006160:Guanosine Triphosphate / Q000378:metabolism; D006868:Hydrolysis; D007700:Kinetics; D008869:Microtubule-Associated Proteins / Q000378:metabolism; D008870:Microtubules / Q000378:metabolism* / Q000648:ultrastructure; D008954:Models, Biological; D009010:Monte Carlo Method; D058105:Polymerization; D014404:Tubulin / Q000378:metabolism* / Q000648:ultrastructure
chemical_list: D008869:Microtubule-Associated Proteins; D014404:Tubulin; D006153:Guanosine Diphosphate; D006160:Guanosine Triphosphate