The CPK R – PE Labeling Kit is ideally suited to label antibodies. In practical applications, the sensitivity of R-PE conjugates is usually 5 to 10 times greater than those of the corresponding fluorescein conjugates. R-PE, a fluorescent protein from phycobiliprotein family, has broad absorption bands with peaks at 565 nm (eM =1.96 X 106 M-1cm-1), 498 (eM =1.53 X 106 M-1cm-1), and 539 nm (eM =1.62 X 106 M-1cm-1); The CPK R – PE Labeling Kit contains SH-reactive R-PE. SMCC modified R-PE reacts with the thiol groups of target antibody without the need for additional activation, thus simplifying the conjugation protocol. The amount of R-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 R-PE are also available as separate products.