Fig. 2.

The fraction, F_v, of free virus in mucus calculated by the difference equation approach decreases with increasing magnitude of the association constant, K_mucin, for binding of virus to mucin and is strongly affected by the local virus to mucin molecule ratio which is set to 2:1 (dash-dotted line), 1:1 (dashed line), 1:2 (dotted line) and <0.1:1 (solid line). The solid line is also represented by Eq. 8 for fully dispersed virus with [Muc_free] = 1.18 × 10⁻⁷ M. In a) the y-axis is linear to visualise the effect for the 2:1 virus:mucin ratio. In b) the y-axis is logarithm transformed to visualise small fractions of F_v as the virus becomes more dispersed in the mucus.