Detection of DYKDDDDK (FLAG^®) in HEK293 Human Cell Line Transfected with DYKDDDDK-tagged Proteins by Flow Cytometry. HEK293 human embryonic kidney cell line transfected with DYKDDDDK-tagged proteins was stained with Rabbit Anti-DYKDDDDK Alexa Fluor® 647-conjugated Antigen Affinity-purified Monoclonal Antibody (Catalog # IC8529R, filled histogram) or rabbit IgG Alexa Fluor® 647 isotype control antibody (open histogram). To facilitate intracellular staining, cells were fixed with Flow Cytometry Fixation Buffer (Catalog # FC004) and permeabilized with Flow Cytometry Permeabilization/Wash Buffer I (Catalog # FC005). View our protocol for Staining Intracellular Molecules.