Difference between Western Blotting and Immunoprecipitation?

[tonyz06]

Hey,
this may be a stupid question, but what are the advantages of immunoprecipitation then immunoblotting compared to western blotting only?

Does it help get less abundant proteins with IP then IB?

Isn't is not enough to just use western blot for protein levels and regulation of protein level?

[danfive]

Immunoprecipitation followed by immunoblotting will help verify the IP, and identify the band (if more than one) that contains the protein of interest, the IP will also deplete or wash away the major non-specific proteins which is very useful if you are going to use MS for further protein ID.

If purity and protein isolation are not necessary, then most likely Western Blot will work best. The only exception I can think of is if the protein is very large or hydrophobic or generally has trouble migrating on the gel---with this situation monitoring a single (Immunopurified) band on the gel will give you an easy test for protein migration on the gel.