Immunoprecipitation

What is immunoprecipitation?

Immunoprecipitation (IP) uses antibody–antigen interactions to isolate small amounts of target proteins or other biomolecules from a mixture for analysis. Often the target molecule is an antigen, captured by incubation with an antibody that binds both the antigen and a ligand immobilized on a matrix such as agarose beads. Two common IP methods are direct capture and indirect capture.

• Direct method = pre-immobilized antibody approach: In this method, the antibodies are attached to the beads in advance. The direct method gives you better control of the antibody binding and immobilizes the antibodies covalently to the beads. This way, you can make sure that the antibodies will not elute and interfere with the subsequent analysis.
• Indirect method = free antibody approach: In this method, antibodies are incubated with the antigen before beads are added. The indirect method is very easy to use, has fewer steps, and can be used if the antibodies do not interfere with following steps.

What can I use immunoprecipitation for?

Use immunoprecipitation to isolate proteins or other biomolecules from cell or tissue lysates before detection by western blotting or before liquid chromatography or mass spectrometry. You can also use IP for rapid, small-scale purification of multiple samples in parallel, as in antibody screening experiments.

Immunoprecipitation column FAQs

Below are answers to some frequently asked questions about immunoprecipitation columns.

What are the applications of immunoprecipitation columns?

Use Cytiva’s immunoprecipitation columns to prepare protein samples before downstream protein analyses such as gel electrophoresis, liquid chromatography, and LC-MS. Cytiva offers protein A and protein G columns and plates, which bind IgG proteins from various species.

Why are beads used in immunoprecipitation?

During immunoprecipitation, beads coupled to a ligand that binds the target molecule are incubated with a solution, such as cell extract or lysate, to allow binding. The beads are then separated from the solution through centrifugation. Agarose beads offer high antibody binding capacity, while magnetic beads allow easy handling and short processing times. However, magnetic agarose beads provide optimal handling and binding capacity.