Schematic representation of the Langevin dynamics system. (a) Schematic representation of the simulation systems. Each system is a rectangular box with hard-wall boundaries and a fence along the Y-axis centered at X = 0. PIP2 molecules are modeled as charged spheres and initially placed inside the pool (X < 0) at a concentration of 6%; the 329 PIP2 from one of the septin simulations are shown explicitly (see Figure S3 for snapshots at later times). (B-C) Schematic representations of two types of rod-like fences, with PIP2 and fence particles enlarged for clarity (b) A porous fence is generated from uncharged blocking atoms on the diffusion plane with a variation in the fence opening length (L open). (c) An electrostatic fence is generated from the single-lined charged atoms placed above the diffusion plane with a variation in the height (h) from the diffusion plane and charge per atom (q).