Tracking individual kinesin motors in living cells using single quantum-dot imaging.

We report a simple method using semiconductor quantum dots (QDs) to track the motion of intracellular proteins with a high sensitivity. We characterized the in vivo motion of individual QD-tagged kinesin motors in living HeLa cells. Single-molecule measurements provided important parameters of the motor, such as its velocity and processivity, as well as an estimate of the force necessary to carry a QD. Our measurements demonstrate the importance of single-molecule experiments in the investigation of intracellular transport as well as the potential of single quantum-dot imaging for the study of important processes such as cellular trafficking, cell polarization, and division.