Fig. 5.

Overview of the system states and their transitions. Representation of three classes of stable conformational states of the SBS polymer chain shown in Fig. 1: (Left) the open random coil (c_m = 5 nmol/L; c_m < C_tr), (Center) the transition-point fractal (c_m = 10 nmol/L; c_m around C_tr), and (Right) the compact globule state (c_m = 25 nmol/L; c_m > C_tr). The polymer conformations were obtained from MC simulations of the SBS model. For clarity, the polymer binding molecules are not shown and the surrounding transparent sphere represents the nucleus. Polymer and sphere sizes are proportional to the size of mammalian chromosomes and nuclei, respectively. Switch-like conformational changes occur, regulated by increasing c_m or E_X above precise threshold values marking thermodynamic phase transitions.