Abrupt buckling transition observed during the plectoneme formation of individual DNA molecules.
The response of single DNA molecules to externally applied forces and torques was directly measured using an angular optical trap. Upon overwinding, DNA buckled abruptly as revealed by a sharp extension drop followed by a torque plateau. When the DNA was held at the buckling transition, its extension hopped rapidly between two distinct states. Furthermore, the initial plectonemic loop absorbed approximately twice as much extension as was absorbed into the plectoneme upon each additional turn. The observed extension change after buckling and the postbuckling torque support a recent DNA elasticity model.
Department of Physics, Laboratory of Atomic and Solid State Physics, Cornell University, Ithaca, New York 14853, USA.
Scott
S
Forth
Christopher
C
Deufel
Maxim Y
MY
Sheinin
Bryan
B
Daniels
James P
JP
Sethna
Michelle D
MD
Wang
D004247:DNA / Q000737:chemistry*; D004278:DNA, Superhelical / Q000737:chemistry*; D008956:Models, Chemical; D009690:Nucleic Acid Conformation
D004278:DNA, Superhelical; D004247:DNA