Figure 4.

Abrupt change in the linker DNA excess twisting, ΔTw, caused by increase in the inclination angle ρ. For ρ = 60° (pink ribbon) the linker DNA is undertwisted by ∼180°. For ρ = 70° (black wire) the linker DNA is overtwisted by ∼180°. The nucleosomes on the left are superimposed. The images were prepared with the Chimera software package (46). Inset: the DNA twisting differs by one helical turn (∼360°) in the two linkers. Compare the black wires representing ∼2.5 turns of DNA in the case of ρ = 70° with the pink ribbons corresponding to ∼1.5 helical turns (ρ = 60°). To see this figure in color, go online.