There is no cooperativity. No ligand depletion. The basic analysis methods assume that only a small fraction of ligand binds. Since homologous competition curves are best performed with low concentrations of radioligand, it may be difficult to comply with this assumption. A later section in this chapter explains how to analyze data when this assumption is not valid.
Nonspecific binding is proportional to the concentration of labeled ligand.
We assume that a certain fraction of hot ligand binds nonspecifically, regardless of the concentration of unlabeled ligand. This assumption has proven to be true in many systems. Theory of homologous competition binding Start with the equation for equilibrium binding to a single class of receptors. K d are in concentration units. Those units cancel so it doesn't matter if you use molar, nM, or some other unit, so long as you are consistent.