CF488A streptavidin conjugate is prepared from high quality streptavidin and the green fluorescent dye CF488A. CF488A (Ex/Em = 490/515 nm) 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.