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A radioligand is a radioactively labeled drug that can associate with a receptor, transporter, enzyme, or any protein 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. Radioligand binding experiments are easy to perform, and provide useful data in many fields. But many find it difficult to analyze radioligand binding data. That's why I wrote this guide.

More information
curvefit.com (extensive web site).
Learn more about our program, GraphPad Prism; the best general-purpose nonlinear regression program for Windows and Mac.

• Assumptions inherent in the law of mass action

Saturation binding experiments

• Nonspecific binding
• Fitting a curve to determine Bmax and Kd
• Scatchard plots
• Why you shouldn't analyze data with Scatchard plots

Competitive binding experiments

• What is a competitive binding curve?
• Performing the experiment
• Analyzing competitive binding data
• Homologous competitive binding curves

Kinetic binding experiments

• What is a dissociation binding experiment?
• How to analyze dissociation experiments
• Using a dissociation experiment to confirm the law of mass action
• Displaying dissociation data on a log plot
• Association rate experiments
• Combining association and dissociation data

Two binding sites

• Competitive binding with two sites
• Analyzing saturation binding experiments with two sites
• Comparing one- and two-site models

Advanced topics

• The slope factor or Hill slope
• Agonist binding
• Ligand depletion

Calculations with Radioactivity

• Efficiency of detecting radioactivity
• Specific radioactivity
• Calculating the concentration of the radioligand
• Radioactive decay
• Counting error and the Poisson distribution