Observing the mushroom-to-brush transition for kinesin proteins

Area of Science:

• Polymer Physics
• Biophysics
• Surface Science

Background:

• Polymer chains grafted to surfaces exhibit distinct conformational states based on their surface density.
• The "mushroom" regime describes polymers at low densities with height independent of density.
• The "brush" regime describes polymers at high densities where height increases with density.

Purpose of the Study:

• To experimentally investigate the polymer mushroom-to-brush transition.
• To explore this transition using kinesin-1 proteins adhered to a surface at controlled densities.

Main Methods:

• Kinesin-1 proteins were adhered to a surface at controlled densities.
• Fluorescently labeled microtubules were attached to the kinesin proteins.
• Kinesin height was measured using fluorescence interference contrast microscopy.

Main Results:

• Experimental measurements were consistent with the predicted "mushroom" regime at low densities.
• Measurements also aligned with the "brush" regime at high densities.
• A transition between the mushroom and brush regimes was observed near the theoretically predicted density.

Conclusions:

• The study experimentally validates the theoretical mushroom-to-brush transition for grafted polymers.
• This transition may influence protein behavior in crowded cellular environments.
• The transition could be utilized for intracellular regulation and mechanotransduction signaling.