Figure 4.

(a) The probability that the virus undergoes endocytosis is plotted as a function of the normalized fusion rate, k_f/p₁, for different values of the normalized coreceptor binding rate, q₁/p₁. The probability of endocytosis decreases with increasing fusion rate and, for a given fusion rate, the probability of endocytosis increases with decreasing q₁/p₁. In this example, the normalized endocytosis rate, k_e/p₁ = 1. (b) For q₁/p₁ = 1, the probability of endocytosis is plotted as a function of fusion rate for different values of the normalized endocytosis rate, k_e/p₁. In both plots, the number of receptor-binding spikes and the number of coreceptor-binding spikes are set to M = N = 100.