Protein interactions with small molecules. Relationships between stoichiometric binding constants, site binding constants, and empirical binding parameters.

The multiple equilibria for the binding of a ligand A by a macromolecule P with n binding sites may be formulated in terms of a stoichiometric analysis or on the basis of a siteoriented scrutiny.The dependence of binding on ligand concentration can always be correlated in terms of n stoichiometric'binding constants, Ki, even if there are interactions between sites that accentuate or attenuate binding afhnities.A corresponding correlation in terms of site binding constants, kj, under the most general circumstances depends on the definition of nZnml difierent constants of which Zn -1 are independent.If experimental data are correlated in terms of R parameters k,, & . . .kx in an equation of the site-binding form,