Phosphorylation is a common modification of proteins that can result in alterations in protein function, protein-protein association, cellular localization, and protein-half life. Phosphorylation can occur on threonine, serine, and tyrosine residues. The PY20 monoclonal antibody recognizes phosphorylated tyrosine residues in all species tested (human, mouse, rat, dog, chicken, and frog). The PY20 antibody has been shown to be useful for flow cytometry, immunoprecipitation, Western blotting, and immunofluorescence staining.