Figure 2.

The influence of β on the conformation of a star fiber (A) and a polygon fiber (B) with pentagonal axial symmetry (α = 36 and 108°, respectively). Each fiber contains 10 nucleosomes. The first nucleosome in each fiber is indicated by an asterisk. The nucleosomal repeat length [205 bp (A) and 196 bp (B)] is kept independent of β, which is varied in steps of 36°, corresponding to ∼10 bp/turn of the DNA, and numbered according to the number of increments of 36°. Large, black arrowheads point towards values of β that are not allowed for sterical reasons. Circular, white arrows indicate the coiling direction. The fibers in A and B are oriented with the connecting linker of the first dinucleosome in the viewing direction (y-axis). As the shifting directions of the fibers do not follow the plane of the paper, as indicated by the thick fibers in gray scale, except for β = 0°, their true length cannot be inferred from the figure. (C) Polygon fiber with NRL 210 bp at β(−1). (D) Stacking of nucleosomes at β(5) into two columns with alternating positive and negative linker orientations by reducing the size of α. The fiber in (D) has NRL = 230 bp and α = ∼36°. (E and F) Compressed polygon fibers formed by reducing the size of α. (E) β(+4) is shown from the end (top) and from the side as seen from two different angles. (F) β(−4) seen from the end (top) and from the side. (G) Axial symmetries of the polygon fiber as a function of β at η₂ = 10 and 0°. Bar = 30 nm.