Watching Supercoiled DNA The DNA double helix can undergo additional twisting, or supercoiling, that plays a role in transciption and protein binding, in part by bringing distant DNA locations together. The process forms intertwined loops, called plectonemes, and van Loenhout et al. (p. 94 , published online 13 September; see the Perspective by Sheinin and Wang ) visualized plectoneme dynamics of fluorescently labeled, 21-kilobase tethered DNA molecules using magnetic tweezers to apply twisting forces. Plectonemes could diffuse along the DNA, but move more rapidly if they “hopped”—nucleating a plectoneme at a new position.