Diffusion of messenger proteins resulting from ligand binding to a small focus of receptors on the cell membrane at time t = 0.

<p>By random walk (top panels), there is broad dispersal of the messenger proteins through the cytoplasm. As a result, all information regarding the time and location of ligand binding is lost. By biased random walk (lower panels) due to Coulomb interactions of phophorylated, negatively charged messenger proteins with an intracytoplasmic electric field, the spatial location of ligand binding on the CM is projected onto the NM and the transition time is less than 0.1 second.