Immunoprecipitation (IP) is a method for selectively isolating a particular protein species from a complex protein solution. The technique relies on antigen/antibody recognition (immuno) and the subsequent mass- or affinity-related isolation of the capture/target complex (precipitation). It is the precipitation of the target protein that is referenced by the name: Pull-down assay. Pull-down assays are commonly used to either confirm the presence of a scant protein species or enrich population for a particular protein, as well as to identify natural binding partners for the captured protein. A typical pull-down assay involves the use of a matrix-associated antibody, such as a bead, and various wash and elution steps to ensure the specific preference for the targeted protein of interest.