Studies of Single Molecules in their Natural Form

Single molecule studies make possible the characterization of molecular processes and the identification of biophysical sub‐populations that are not accessible through ensemble studies. We describe tethered particle motion, a method that allows one to study single molecules in their natural form without having to apply any external forces. The method combines darkfield microscopy with a metal nano‐bead. It permits the study of the biophysical properties of the tethered particles, as well as protein–DNA interactions. The method is not suitable for in vivo studies, and we therefore describe two other methods that are appropriate for live‐cell imaging