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. 2016 Jan 5;110(1):218–233. doi: 10.1016/j.bpj.2015.10.045

Figure 4.

Figure 4

Dependence of virus adhesion on HA-SA binding affinity. (Red curve) Fraction of virus particles bound to host cells versus KD of HA-SA binding. (Dark-blue curve) R50 (see text) versus KD. (Light-green region) Interval of viable KD values such that the virus can 1) attach sufficiently to and infect cells and 2) release itself, with the help of neuraminidase, from the cells to spread the infection. The upper bound of the region corresponds to the KD value at which half of the viruses attach to cells; the lower bound corresponds to the KD value at which 99% of all SA moieties must be removed in order for half of the viruses to detach from the cells. (Solid curves) Results from Eqs. 1 and 2, which assume that all SA receptors on the cell bind to the HA molecule with the same affinity KD; (dashed curves) results from Eqs. 16–18, which assume that the binding free energy is uniformly distributed between RTln(KD/10) and RTln(KD10).