Cellular motions and thermal fluctuations: the Brownian ratchet

Citation: C. S. Peskin, G. M. Odell, G. F. Oster (1993).
Link: Zotero

Summary

• Key finding:
• Method:
• Limitations:
• Notes in my words:

Relevance to my research

• Directly relevant
• Background
  • Force production mechanisms of actin polymerization
• Methods

Quotes / Figures

The systems we address here are different from those usually considered protein motors (e.g., myosin, dynein, kinesin), but such motors may be Brownian ratchets as well (1-4).

Parameters:

Symbol	quantity that the symbol represents	expression
$\omega$	The dimensionless work done against the load in adding one monomer	$\omega =f\times \frac{\delta }{k_{B}T}$
$f$	Load force of the barrier (i.e. force that the polymer has to overcome to polymerize)	—
$x$	distance between the tip of the polymer and the barrier	—

Speed of a perfect Brownian ratchet:

$$\boxed{v=\frac{2D}{\delta }}$$

Note that as the ratchet interval, $\delta$, decreases, the ratchet velocity increases.

If no barrier were present, actin could polymerize at a maximum velocity of $\sigma \times R\sim 0.75$ ,um/s at 25 , $\mu$M concentration of actin monomers

Cellular filopodia protrudes at 0.16 $\mu$m /s