Theory 25/Mechanotransduction/Single-molecule force spectroscopy
Force Is Read at a Threshold
The claim
A mechanosensitive protein responds to force only above a threshold set by the ratio of its unfolding energy to the loading rate, so the same cell can be sensitive or blind depending on how fast the force is applied.
01Mechanism
Molecular bonds break stochastically under load; the loading rate determines the force at which rupture becomes likely.
02Prediction
Response threshold should depend on loading rate.
03Refutation
Threshold independent of loading rate would remove the kinetic argument.
04What makes it checkable
Optical tweezers and magnetic tweezers now apply calibrated forces to single molecules while recording their state.
05Why it was not testable before
Force could not be applied and measured at molecular scale until the tweezers matured.