- Biotinylation
- Conjugation to fluorophores
- Protease digestion
- Coupling to bead surfaces
After purification proteins may be modified for use in assays or other applications. Probably the most common protein modifications are labels that are used for immunoassays, flow cytometry, fluorescence-activated cell sorter (FACS) analysis and molecular structure and function studies. A number of different affinity or detectable (e.g., fluorescent) labels are available for covalent coupling to proteins.
Proteins may also be coupled to solid surfaces (latex particles or magnetic beads) for implementation in a variety of assays (drug discovery, diagnostics etc.).
Another popular protein modification is protease digestion. The expression of some proteins, especially small proteins, is often very difficult. By designing a fusion protein with a protease cleavage site between the fusion partners, even small proteins may be expressed and purified. Following digestion with the specific protease the active protein is further purified.
