DNA elasticity

(a) Microscopy images of the pulling experiment (the DNA is not visible).
(b) Force-extension graph of the experiment in panel a. As the DNA is pulled to larger extensions, it undergoes several phases of distinct elastic behavior. The red line is a fit to the so-called worm-like chain model. The overstretching transition, typical for double-stranded DNA, is readily seen.
The DNA samples used were generously provided by Dr. A. Sischka (Anselmetti lab, Bielefeld, Germany).