Figure 2.

Force-extension profiles for fibers with NRL = 167 bp (A) and 197 bp (B) for various degrees of unwrapping of nucleosomes, U, varying from 0 to 32 bp, with stacking energy E = 0. The symbols represent the average extension per nucleosome obtained from MC simulations. The solid curves represent experimental data (15). The circles indicate the points of intersection of the MC curves with the experimental (F, Z_ext) curves in the central plateau region. Simulations were performed for forces from 0 to 8 pN in steps of 0.5 pN. The standard deviation (SD) of the extension, Z_ext, is ∼1 nm at low forces; it shrinks below 0.2 nm at high forces. Curves for U = 5, 60 bp, and free DNA are presented in Fig. S5. To see this figure in color, go online.