Tracking a Molecular Motor with a Nanoscale Optical Encoder

Optical encoders are commonly used in macroscopic machines to make precise measurements of distance and velocity by translating motion into a periodic signal. Here we show how Förster resonance energy transfer can be used to implement this technique at the single-molecule scale. We incorporate a series of acceptor dye molecules into self-assembling DNA, and the periodic signal resulting from unhindered motion of a donor-labeled molecular motor provides nanometer-scale resolution in milliseconds.