 Finally, the beads are released by EGTA, leaving behind the native eluate containing only the protein of interest, its bound protein partners and the remaining CBP piece of the TAP tag.The native eluate can then be analyzed using gel electrophoresis and mass spectrometry to identify the protein's binding partners.An advantage of this method is that there can be real determination of protein partners quantitatively in vivo without prior knowledge of complex composition.