Nucleosome structure twist model

One result of the simulations was that the torsion angle q> between successive nucleosomes determines the properties of the structure to a great extent (as also predicted by the two-angle model). While a variation in the internucleosome interaction potential by a factor of four changes that simulated mass density by only about 5%, this quantity is very sensitive to variations in twist angle (see Fig. 6 in Ref. [50]). 

Studies of the condensed chromatin fibre structure and the condensation mechanism have resulted in basically two classes of models models based on a helical arrangement of nucleosomes along the fibre and those based on a linear array of globular nucleosome clusters (superbeads) along the fibre. The first class includes the solenoid, twisted ribbon and crossed linker models whereas the latter are the superbead models and related layered structures. Schematic representations of some models are shown in Fig. 10. 

In the twisted ribbon models the low ionic strength structure of chromatin is described by a flat ribbon consisting of two parallel stacks of nucleosomes... 

---