Bistable system with diffusion.

<p>(A) Schematic of diffusing molecules in volume <i>V</i>. (B) Snapshot of cubic reaction volume for generalized Schlögl model as simulated with <i>Smoldyn</i> software [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0121681#pone.0121681.ref038" target="_blank">38</a>]. Shown are monomers <i>X</i> in red and dimers <i>X</i>₂ in green. Clustering is illustrated by red dashed outline. (C) Chemical reactions of generalized Schlögl model. (D) Time trace (left) and histogram (right) of <i>x</i> = <i>X</i>/<i>V</i> from simulation for <i>D</i> = 3 (for <i>X</i>) and 1 (<i>X</i>₂), <i>V</i> = 10, <i>k</i>₊₃ = <i>k</i>₋₃ = 1, and <i>B</i> = 3.7. (E) and (F) Effects of reduced (times 0.1) diffusion constants (E) and increased (times 2) volume (F). In (E) <i>B</i> = 3.1 to achieve comparable weights of low and high states. (G) Schematic of localized transcription in self-activating gene pathway. (H) Snapshot of spherical reaction volume with cylindrical DNA (purple) as simulated with <i>Smoldyn</i>. Shown are monomers in red and dimers in green with illustration of clustering by red dashed outline. (I) Histogram of monomer concentration <i>x</i> from simulation for <i>V</i> = 2.14 and <i>V</i>_DNA = 1.51, <i>D</i> = 30 (<i>X</i>) and 10 (<i>X</i>₂), <i>k</i>₊₁ = <i>k</i>₊₂ = 50 and <i>B</i> = 50.