Receptor spacing, affinity zone size and clustering. A) Cartoon representing clusters of receptors with different receptor size width (r) on affinity zone width (b) ratio. A fixed affinity zone as it was used in simulation with a increasing receptor width leads to an increasing r/b ratio and therefore to sparser clusters of receptors. B) Ratio of fitted EC50 to control EC50 (i.e. for n = 1) with increasing cluster size, with contiguous receptors and with respect to receptor width on affinity zone width ratio. The scale is semi-logarithmic.