AAT Bioquest's iFluor® dyes are optimized for labeling proteins, in particular, antibodies. These dyes are bright, photostable and have minimal quenching on proteins. They can be well excited by the major laser lines of fluorescence instruments (e.g., 350, 405, 488, 555 and 633 nm). iFluor® 555 dyes have fluorescence excitation and emission maxima of ~550 nm and ~570 nm respectively. iFluor® 555 family has the spectral properties essentially identical to those of Cy3® (Cy3® is the trademark of GE Healthcare). Compared to Cy3 probes iFluor® 555 family has much stronger fluorescence and higher photostability. Their fluorescence is pH-independent from pH 3 to 11. These spectral characteristics make this new dye family a superior alternative to Cy3®. iFluor® 555 family has become an excellent replacement for Cy3 and Alexa Fluor® 555 labeling dye (Alexa Fluor® is the trademark of Invitrogen). ReadiLink™ labeling kits essentially only require 2 simple mixing steps without a column purification needed. iFluor® 555 SE used in this ReadiLink™ 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® 555 dye provided in the kit is optimized for labeling ~50 µg antibody. iFluor® 555 SE protein labeling kit provides a convenient method to label monoclonal, polyclonal antibodies or other proteins (>10 kDa) with the iFluor® 555 SE.