Figure 1. A polymer model of chromatin.

(a) The Strings&Binders (SBS) model is a Self-Avoiding (SAW) chain of beads interacting with molecular binders having a concentration, c, and a binding affinity E_Int. (b) Polymer physics dictates that the model different stable architectural classes correspond to the different phases of its phase diagram: at low E_Int or c, the polymer is open and randomly folded in its coil phase; above its Θ-point transition, in the globule phase it is closed in more compact conformations as signalled by a drop in its gyration radius (Figure S1a); in the closed state, at higher values of E_Int or c, its binders have a transition form a disordered to an ordered arrangement, as shown by their Structure Factor (Figure S1b).