Figure 5. Rapid ligand-induced localization of receptors within lipid rafts due to a ligand-induced change in dimerization kinetics of receptors.

Simulation was initiated with randomly distributed receptors on the membrane. Receptors were allowed to equilibrate between monomer and dimer states in the absence of ligand with k_mono = 10⁶ s⁻¹ and k_dimer = 10⁶ s⁻¹. Ligand with concentration [L] = K_d = k_r/k_f was then added and simulations continued until a steady state was reached; k_f = 10⁸ M⁻¹s⁻¹ and k_r = 1 s⁻¹. Ligand-bound receptors were assumed to have the same monomerization rate constant as the unligated state but k_dimer was decreased to 10⁴ s⁻¹. Simulations were run on a membrane including lipid rafts with total area of 10% and diameter of 20 nm. Diffusion coefficients in lipid raft and non-raft regions were 10⁻¹¹ cm²/s and 10⁻¹⁰ cm²/s respectively.