Appendix. On the applicability of Hill type analysis to fluorescence data.

Ligand binding properties of macromolecules are described by the number of binding sites, values of binding constants, and, possibly, cooperativity between sites.This information can usually be derived from Scatchard (1) and/or Hill plots (2) (for a review, see Ref. 3).When the fraction of sites occupied at a given concentration of ligand cannot be measured directly, as is the case in the accompanying paper (4),