AAT Bioquest's iFluor(TM) 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(TM) 555 dyes have fluorescence excitation and emission maxima of ~550 nm and ~570 nm respectively. iFluor(TM) 647 family has the spectral properties essentially identical to those of Cy5(R) (Cy5(R) is the trademark of GE Healthcare). Compared to Cy5 probes iFluor(TM) 647 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 an excellent alternative to Cy5(R) and Alexa Fluor(R) 647 (Cy5(R) and Alexa Fluor(R) are the trademark of Invitrogen and GE Health Care). iFluor(TM) 647 amine is stable and used for modifying carbonyl groups (e.g., aldehyde and carboxy groups).