Co-immunoprecipitation, Co-IP in short, is a widely applied technique to identify physiologically-relevant protein-protein interactions by utilizing target protein-specific antibodies to indirectly capture proteins that are bound to this specific target protein. A an extension of IP, co-IP can capture and purify not only the primary target, but also other macromolecules binding to the target by native interactions. Thus whether an experiment is called an IP, or co-IP depends on whether the focus of the experiment is the primary target (antigen) or secondary targets (interacting proteins). Then the precipitated proteins can be eluted and characterized in various methods, such as WesternBlot and mass spec analysis under shotgun strategy, to identify partner protein IDs, binding affinities, kinetics of binding and undiscovered functions of the primary protein.

As a powerful technique, co-IP is utilized regularly by biochemists to explore protein–protein interactions. While the co-IP methodology is straightforward, identifying physiological protein-protein interactions through co-IP reaction is not easy, because of the instability of the interaction, nonspecific binding to IP reagents and antibody contamination. All of the problems above can have negative effects on detection of protein-protein interactions. Creative Proteomics can provide more reliable studies of protein-protein interactions with our experienced scientists and technicians.

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