Germanium nanospheres for ultraresolution picotensiometry of kinesin motors

Kinesin takes substeps Simultaneously measuring the nanoscale motion and forces that molecular machines generate provides insights into how they work mechanically to fulfill their cellular function. To study these machines, Sudhakaret al. developed germanium semiconductor nanospheres as probes for so-called optical tweezers. With these high–refractive index nanospheres, they improved the resolution of optical tweezers and discovered that the motor kinesin takes 4-nanometer substeps. Further, instead of detaching from their microtubule track under load, motors slid back on it, enabling rapid reengagement in transport. The new technology will allow investigation of a range of other proteins and their behaviors at nanometer scales.Science , this issue p.eabd9944