A radioligand is a radioactively labeled drug that can associate with a receptor, transporter, enzyme, or any site of interest. Measuring the rate and extent of binding provides information on the number of binding sites, and their affinity and accessibility for various drugs.

There are three kinds of experimental protocols, discussed in the next three chapters.

Saturation binding experiments measure equilibrium binding of various concentrations of the radioligand. Analyze the relationship between binding and ligand concentration to determine the number of sites, Bmax, and the ligand affinity, Kd. See Introduction to saturation binding experiments

Competitive binding experiments measure equilibrium binding of a single concentration of radioligand at various concentrations of an unlabeled competitor. Analyze these data to learn the affinity of the receptor for the competitor. See What is a competitive binding curve?

Kinetics experiments measure binding at various times to determine the rate constants for radioligand association and dissociation. See Dissociation ("off rate") experiments and Association binding experiments.

Prism makes it easy to analyze and display data from all three kinds of experiments.

For more information on analysis of radioligand binding data, see:

LE Limbird, Cell surface receptors: A short course on theory and methods, Martinus Nijhoff Publishers, second edition, 1996. Order from amazon.com.

HI Yamamura, et al, Methods in Neurotransmitter receptor analysis, Raven Press, 1990 (Out of print, check your libarary)