Experimentally measured phonon spectrum of microtubules

Microtubules are self-assembled protein cylinders with important mechanical roles inside living cells. Here we present an experimental method to measure the transversal collective dynamic modes of taxol stabilized microtubules in vitro. We treat the microtubule as a lattice of particles interacting with harmonic potentials and we use Fourier decomposition of the shape of the microtubule under excitation from thermal energy. We report the phonon spectrum due to these modes in MHz frequencies and the sound velocity is in the order of mm s⁻¹. (paper)