coimmunopresipitering

Co-immunoprecipitation (co-IP), sometimes spelled co-immunopresipitering in some languages, is a biochemical technique used to study protein-protein interactions. By capturing a target protein (the bait) with a specific antibody, co-IP isolates the bait together with any proteins bound to it (the prey) from a cell lysate. This approach preserves native complexes under conditions that maintain interactions, allowing for the study of protein networks.

The typical workflow involves lysing cells under non-denaturing conditions, incubating the lysate with an antibody coupled to a solid support such as beads, immunoprecipitation of the antibody-protein complex, washing to remove non-specifically bound proteins, and elution of the immune complex for analysis.

The co-immunoprecipitated proteins are detected by subsequent analyses, most commonly Western blotting with antibodies against suspected interactors, or by mass spectrometry for broad identification. Experimental design includes appropriate controls (such as an isotype control or lysate-only control) and consideration of lysis buffer composition, salt concentration, and potential crossreactivity.

Variants include using epitope-tagged bait proteins to simplify capture, and crosslinking to stabilize transient interactions, though crosslinking can introduce artifacts. Co-IP is widely used to validate interactions suggested by other methods and to map components of protein complexes.

Limitations include potential loss of weak or transient interactions, dependence on antibody quality and epitope accessibility, and risk of co-purifying non-specific proteins. Proper controls, replication, and orthogonal methods are essential to interpret results.