Immunoprecipitation and western blotting are both used to locate a specific protein within a sample and to isolate it. In immunoprecipitation, a specific antibody and agarose beads ( or other insoluble beads) are used to precipitate the protein. In western blotting, SDS-PAGE is carried out and primary and secondary antibodies are used to locate and isolate the proteins on the nylon membrane.

My question is: which technique should be used when? what is the difference between the two? is one of them "better" / does one of them have advantages over the other?


The two techniques serve different purposes:

IP: purifies a protein

WB: visualizes or quantifies a protein

Most often when I have done IPs (in the hazy past) I have turned around and run the protein out on a WB, so one will frequently combine both techniques. Sometimes a protein is very low abundance so you will not see it in a small volume of crude cell lysate on a WB, and you have to IP it from a large number of cells to get enough protein to visualize on a WB.

Note that IPs will also co-purify associated proteins, so a good way to know whether two proteins stick together is to IP one of them and probe for the other on a WB. This "co-IP" analysis is a very common use case for both techniques.

Hope that helps.


Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.