Protein A and Protein G are proteins that readily bind the Fc regions of many types of antibodies. For this reason, they are used extensively for affinity purification of antibodies from serum or cell culture supernatant, and for capture of immunoprecipitated protein complexes. When Protein A and Protein G microspheres are used as reagents in tests and assays, the immobilized antibodies may be crosslinked to the Protein A- or Protein G-coated support for long-term stability. Protein A and Protein G coated microspheres are available as ~1% solids (w/v) aqueous suspensions in these standard volumes: 1mL, 2mL, 5mL, or 10mL.