We present a single curve that describes the decay in average growth velocity for microtubules in response to a mechanical force. Curves obtained at two new and one previously studied tubulin concentrations coalesce when normalized with the growth velocity at zero load. This scaling provides direct evidence for a force-independent molecular off rate, in agreement with Brownian ratchet models. In addition, microtubule length changes were measured with a precision up to 10 nm, revealing that microtubules under load abruptly switch between different growth velocities.

Phys. Rev. Lett.

Janson, M., & Dogterom, M. (2004). Scaling of microtubule force-velocity curves obtained at different tubulin concentrations. Phys.Rev.Lett., 92(Article number: 248101), 1–4. doi:10.1103/physrevlett.92.248101