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. 2009 May 6;96(9):3708–3715. doi: 10.1016/j.bpj.2009.01.048

Figure 1.

Figure 1

Schematic representation of a magnetic tweezers experiment on a DNA-nucleosome complex. (a) A DNA molecule containing a single nucleosome is attached between a magnetic bead and a glass coverslip. The force is controlled by changing the distance between the bead and two external magnets above the sample. DNA unwrapping from the nucleosome under force occurs in two distinct steps (a to b, then b to c). Two typical examples of experimental DNA unwrapping traces at 2 pN (d) and at 6 pN (e), where unwrapping is accompanied by an increase in end-to-end distance of the DNA-nucleosome complex.