Figure 4. Minimum number of receptors required for stable binding and the influence of receptor diffusion on binding.

The diffusivity of the receptors in the membrane was varied in silico from 1.8 µm²/s (black) to 0.18 µm²/s (light blue) and immobile receptors (dark blue). (A) Reducing the receptor diffusivity reduces the fraction of bound virions and increases the concentration at which stable binding is observed. (B) The mean number of stably bound receptors decreases with decreasing diffusivity of the receptors. (C,D) Analysis of stably bound particles for 0.1 mol% (C) and 1 mol% (D). At 0.1 mol% and the in vitro measured diffusivity of GM1, about 5% of particles are bound with 4–6 receptors each, but significantly less at lower diffusivities. At 1 mol%, virions gather up to 40 and more receptors for the measured diffusivity, less at 0.1 µm²/s and for immobile receptors a single peak is formed.