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Schematic illustration of the conformational changes of a DNA molecule in a magnetic tweezers setup (not to scale). A DNA molecule is tethered between a superparamagnetic bead and a glass surface. Force and torque on the DNA molecule are applied by an external pair of magnets (not shown) to the bead. Here, we consider the coexistence of three states: twisted, plectonemic, and melted DNA. To see this figure in color, go online.
