AFDye 680 (Alexa Fluor ® 680 equivalent) is a bright and photostable near-IR dye that is spectrally identical to Alexa Fluor® 680 and IRDye® 680RD. AFDye 680 is often used for small animal imaging applications in the 700 nm wavelength and provides excellent clearance profiles in animals. Flow cytometry is another common application for this dye. AFDye 680 ideally suited for the 633 nm laser line. This near-IR fluorescent dye is water soluble and pH-insensitive from pH 4 to pH 10. AFDye 680 molecules can be attached to proteins at high molar ratios without significant self-quenching, leading to brighter conjugates and more sensitive detection. The long wavelength emission allows for detection in complex samples with auto-fluorescent background signals.
Maleimide is the most popular sulfhydryl-reactive reactive group for conjugating the dye to a thiol group on a protein, oligonucleotide thiophosphate, or low molecular weight ligand. The maleimide group specifically and efficiently reacts with reduced thiols (sulfhydryl groups, –SH) at pH 6.5 to 7.5 to form stable thioether bonds.