The R-PE Labeling Kit provides a convenient way to conjugate an tibodies to R-Phycoerythrin (R-PE). R-PE belongs to the Phycobiliproteins family of highly soluble and fluorescent proteins derived from cyanobacteria and eukaryotic algae. R-PE is made of α, β and γ subunits and is present as (αβ)6γ. The protein has broad absorption bands with peaks at 496 nm, 546 nm, and 565 nm, and can be excited with versatile excitation sources. The broad excitation spectrum provides the advantage for multi-color immunofluorescence staining and cell sorting. The R-PE Labeling Kit is a SH-reactive labeling kit. Modified R-Phycoerythrin can easily react with SH groups of a t arget antibody without the need for an additional activation, thus simplifying the conjugation protocol. Modified R-PE and sulfhydryl group on the antibody form a covalent bond during conjugation.