An active biopolymer network controlled by molecular motors

Area of Science:

• Biophysics
• Materials Science
• Cell Mechanics

Background:

• Active polymer networks are crucial for understanding cellular mechanics.
• Molecular motors play a key role in regulating the mechanical properties of biological tissues.
• Filamin A (FLNa) and myosin II are essential components in cytoskeletal dynamics.

Purpose of the Study:

• To investigate an active polymer network where molecular motors control elasticity.
• To quantify the stiffening effect of internal stress generated by myosin II motors.
• To compare the mechanical response of the active network to external mechanical shear.

Main Methods:

• Constructing an active polymer network using actin filaments, filamin A (FLNa) cross-links, and muscle myosin II motors.
• Measuring network elasticity and stress generation under motor activity.
• Applying external mechanical shear to compare with internal stress effects.

Main Results:

• Myosin II motors increased network stiffness by over two orders of magnitude.
• Internal stress generation by motors mimicked the stiffening effects of external shear stress.
• The active network exhibited nonlinear stiffening behavior under both internal and external stress.
• Active stress reached 14 Pa, corresponding to approximately 1 pN per myosin head.

Conclusions:

• Active polymer networks with molecular motors can mimic cellular mechanical properties.
• Cells may utilize nonlinear mechanical regimes for stiffness control via motor activity.
• This principle can inform the design of novel, biologically inspired active materials with tunable stiffness.