Single-Molecule Mechanics of DNA - DNA Nanotechnology: From Structure to Function - page 93

Fig. 6.9 The topology of an elastic chain [ 26 ]

Fig. 6.10 The deformation
of dsDNA under external
force stretching (Reprinted
from Ref. [ 21 ]. Copyright
1998, with permission from
Elsevier)

6.2.2.2 Single-Molecule Observation of the Transition from Wr to Tw

In 1996, Strick et al. studied the twist behavior of single molecules of linear dsDNA
by means of magnetic tweezers. They found that the behavior of dsDNA varies
significantly at different external forces (see Fig. 6.10 ). The rotation of the magnetic
bead twists the dsDNA. The rotation round number ( n ) equals to the Lk. The value

of at a given moment can be calculated accordingly [ 21 , 27 ].