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. 2011 Oct 27;7(10):e1002229. doi: 10.1371/journal.pcbi.1002229

Figure 3. The Symmetry Breaking (SB) mechanism.

Figure 3

Top Panel The SB parameter, Inline graphic, is the normalized average difference of type-A molecule density around type-Inline graphic region of polymers Inline graphic and Inline graphic. Its dynamics, from the initial symmetrical polymer looped state (as in the schematic picture in the Bottom Panel, “Stable Interaction”), is shown for two characteristic values of molecule homotypic interaction energy, Inline graphic (here Inline graphic and Inline graphic). If Inline graphic, Inline graphic is close to zero: molecules are equally distributed around the polymers. If Inline graphic, after a transient of about ten hours, Inline graphic approaches one, i.e., either Inline graphic or Inline graphic: molecules have aggregated around only one of the polymers, and their binding symmetry is broken (as in the schematic picture in the Bottom Panel, “Symmetry Breaking”). Bottom Panel The phase diagram in the Inline graphic plane (for Inline graphic) has three phases. If Inline graphic is below the transition line, Inline graphic (red dashed line), the system is in one of its symmetric phases: the “Open State” phase (at low Inline graphic) or the symmetrical “Stable Interaction” phase. If Inline graphic, the conformational symmetry is broken (“Symmetry Breaking” phase): the type-Inline graphic loop persists only on one randomly chosen polymer, and type-Inline graphic on the other.