Crosslinking and depletion determine spatial instabilities in cytoskeletal active matter

Area of Science:

• Biophysics
• Soft Matter Physics
• Cellular Mechanics

Background:

• Active gels composed of cytoskeletal proteins exhibit non-equilibrium properties like self-organization and self-propulsion.
• Previous research identified four distinct spatial patterning instabilities (bending, buckling, global contraction, local contraction) in different active gel systems.

Purpose of the Study:

• To observe all four known spatial instabilities within a single type of active gel.
• To demonstrate that these instabilities are controllable by varying ATP and depletion agent concentrations.

Main Methods:

• Investigated active gels composed of cytoskeletal proteins.
• Systematically varied concentrations of ATP and depletion agents.
• Utilized a hydrodynamic model for viscoelastic active gels to interpret observations.

Main Results:

• Observed bending, buckling, global contraction, and local contraction instabilities in one active gel system.
• Showed that decreasing ATP concentration leads to increased passive motor concentration and gelation.
• Demonstrated that gelation favors buckling over bending and global over local contraction.

Conclusions:

• A unified view of spatial instabilities in cytoskeletal active matter is provided.
• The study links instabilities to a hydrodynamic model with a diverging crosslinking characteristic time as ATP decreases.
• Control over active gel patterning is achieved through tuning ATP and depletion agent concentrations.