Tethered particle motion with single DNA molecules

A simple method for tethering microbeads using single molecules of DNA is explained. We describe how to use video microscopy and particle tracking to measure the trajectories of the microbeads' motion. The trajectories are analyzed and compared to different models of tethered particle motion. In addition, the data are used to measure the elasticity of the DNA (its spring constant), and the DNA persistence length. (C) 2015 American Association of Physics Teachers.