Fig. 2.

Conceptual picture illustrating the projection of a mixture of brightness species into two different classes. One class contains the molecules of A that are not interacting with D, which is referred to as free species (A,A₂,…,A_r). The other class includes all species that contain the molecule D (D,DA,DA₂,…,DA_s) and is called heterospecies. The analysis method that accomplishes the separation is described in the text. The FFS parameters describing the heterospecies characterize the binding between D and A.