The AnaTag™ B-PE Labeling Kit is optimized for use in the conjugation of B-Phycoerythrin (B-PE) to antibodies. B-PE, a fluorescent protein from phycobiliprotein family, has a primary absorption peak at 545 nm with a secondary peak at 563 nm and maximum emission at 578 nm. B-PE and the closely related R-PE are the most intensely fluorescent phycobiliproteins having orange fluorescence. They are significantly brighter and more photostable than conventional organic fluorophores. B-PE labeled primary and secondary antibodies are used in applications such as flow cytometry and multi-color immunofluorescent staining. The AnaTagTM B-PE Labeling Kit contains SH-reactive B-PE. SMCC modified B-PE reacts with the thiol groups of target antibody without the need for additional activation, thus simplifying the conjugation protocol. The amount of B-PE supplied in this kit is sufficient for labeling up to 1 mg of antibody. The kit provides all reagents, purification columns and a detailed step-by-step protocol. Native and SMCC-activated B-PE are also available as separate products.