The Theoretical Basis for Characterizing Receptors Using Saturation Radioligand Assays

2b The Theoretical Basis for Characterizing Receptors Using Saturation Radioligand Assays. Radioreceptor assays were first developed in the early 1970s. They were based on two simple, but very elegant, concepts. 

If a ligand had high affinity for a macromolecular target (as had been shown by classical pharmacological studies over many decades), it should be thermodynamically possible to measure the binding of the ligand to the receptor without 

By labeling ligands with appropriate radioactive atoms, one could detect the ligand-receptor sensitively and rapidly. (This was the key point, since chemical methods were neither sufficiently sensitive, nor inexpensive, for this use.) 

We begin with the simple law of mass action shown in Eq. (19.1)  

It is useful to replace some of these terms with equivalent ones that are common lab jargon in the held and that reflect the measurements that are actually made in characterizing receptors. These names are as follows  

---