APTBIO offers high sensitivity protein identification from solution (of IP, Co-IP or Pull-down) samples using the latest technologies in mass spectrometry.
Immunoprecipitation, IP in short, is the technique of precipitating a protein antigen out of solution using an antibody that specifically binds to that particular protein. This process can be used to isolate and concentrate a particular protein from a sample containing many thousands of different proteins. Immunoprecipitation requires that the antibody be coupled to a solid substrate at some point in the procedure.
Immunoprecipitation of intact protein complexes (i.e. antigen along with any proteins or ligands that are bound to) is known as co-immunoprecipitation (co-IP). Co-IP works by selecting an antibody that targets a known protein that is believed to be a member of a larger complex of proteins. By targeting this known member with an antibody it may become possible to pull the entire protein complex out of solution and thereby identify unknown members of the complex. Co-IP is a powerful technique that is used regularly by molecular biologists to analyze protein-protein interactions.
Pull-down assays probe interactions between a protein of interest that is expressed as a fusion protein (e.g., bait) and the potential interacting partners (prey). In a pull-down assay one protein partner is expressed as a fusion protein (e.g., bait protein) in E. coli and then immobilized using an affinity ligand specific for the fusion tag. The immobilized bait protein can then be incubated with the prey protein. The source of the prey protein can be either from a cell-based or cell-free expression system. After a series of wash steps the entire complex can be eluted from the affinity supporting using SDS-PAGE loading buffer or by competitive analyte solution, then evaluated by SDS-PAGE.
1) Protein identification results
2) Peptides identification results