Dynamic instability of a growing adsorbed polymorphic filament.

Area of Science:

• Biophysics
• Polymer Science
• Cell Biology

Background:

• Dynamic instability, characterized by intermittent transitions between slow growth and rapid shrinkage, is a crucial feature of polymeric assemblies such as microtubules and actin.
• This labile phase has significant functional implications in cytoskeletal dynamics and its recurrent evolution suggests inherent simplicity.

Purpose of the Study:

• To identify the minimal requirements for dynamic instability in a single polymorphic filament.
• To explore the phase space of filament behavior controlled by structural and kinetic parameters.

Main Methods:

• Modeling a single polymorphic filament that grows, undergoes conformational change, and may unbind due to induced strains.
• Identifying and analyzing two key parameters: a structural mechanical parameter and a kinetic parameter.

Main Results:

• Two parameters, structural (bond strength ratio) and kinetic (timescale ratio), control filament behavior.
• In the deterministic limit, these parameters separate growth from collapse.
• Disorder in these parameters leads to coexistence of growth and collapse phases, exhibiting dynamic instability.

Conclusions:

• Dynamic instability emerges from the interplay of structural and kinetic parameters, particularly in the presence of disorder.
• A phase diagram quantifies the conditions and evolvability of dynamic instability.
• Understanding these minimal ingredients provides insights into the fundamental mechanisms of cytoskeletal dynamics.