This protein labeling kit comprises the green fluorescent dye CF488A in succinimidyl ester (SE) form and other necessary materials for labeling 3×1 mg antibody. CF488A is a superior alternative to the traditional green fluorescent dye FITC (or fluorescein) owing to its exceptional brightness and photostability. CF488A has brightness and photostability comparable to Alexa Fluor 488. However, protein conjugates prepared from CF488A are more specific than those prepared from Alexa Fluor 488 because CF488A, being minimally charged, does not significantly change the isoelectric points of the proteins as Alexa Fluor? 488 does (please download the CF488A dye flyer for more details).