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 to Cy3 and Alexa Fluor 555 labeling dye （Cy3 and Alexa Fluor are the trademark of Invitrogen and GE Health Care）。 iFluor 555 hydrazide is reasonably stable and shows good reactivity and selectivity with carbonyl group （such as aldehyde）。
