Ex (nm) 491, Em (nm) 514. Although FITC is still the most popular fluorescent labeling dye for preparing green fluorescent bioconjugates, there are certain limitations with FITC, such as severe photobleaching for microscope imaging and pH-sensitive fluorescence. Protein conjugates prepared with iFluor(TM) 488 dyes (Ex/Em=497 nm/525 nm) are far superior compared to conjugates of fluorescein derivatives such as FITC. iFluor(TM) 488 conjugates are significantly brighter than fluorescein conjugates and are much more photostable. Additionally, the fluorescence of iFluor(TM) 488 is not affected by pH (4-10). This pH insensitivity is a major improvement over fluorescein, which emits its maximum fluorescence only at pH above 9. ReadiLink(TM) labeling kits essentially only require 2 simple mixing steps without a column purification needed. iFluor(TM) 488 SE used in this ReadiLink(TM) kit is reasonably stable and shows good reactivity and selectivity with protein amino groups. The kit has all the essential components for labeling ~2x50 ug antibody. Each of the two vials of iFluor(TM) 488 dye provided in the kit is optimized for labeling ~50 µg antibody. iFluor(TM) 488 SE protein labeling kit provides a convenient method to label monoclonal, polyclonal antibodies or other proteins (>10 kDa) with the iFluor(TM) 488 SE.