Immunoprecipitation is a technique for the isolation of protein or a complex (protein-protein interactions) Sample is combined with a specific antibody for the epitope of interest. The antibody-protein complex is removed and analysed.

1. Molecules from biological sample (lysed) +incubated with antibodies (free or mounted onto support (like agarose bead, magnetic bead))
2. protein A or G coupled beads added.
3. Centrifuged
4. Results in Beads with protein A/G bound to antibody-POI complex.
5. Well separated in this way, differentially based on sedimentation coefficient.

Co-immunoprecipitation (can isolate one type of protein in its complex)

Isolate POI(s) Good with low conc. of POI Protein interactions Unknown proteins Determine if protein is actually being expressed in a given tissue.

Western blot is carried out to analyse the output.

Vary salt and detergent levels to preserve or destroy protein interactions.