pHAb Dye is a pH sensor dye that have very low fluorescence at pH > 7 and a dramatic increase in fluorescence as the pH of the solution becomes acidic. pHAb Dyes have excitation maxima (Ex) at 532nm and emission maxima (Em) at 560nm. pHAb Dyes are designed specifically for antibody labeling. pHAb Amine Reactive Dye has a succinimidyl ester group that reacts with primary amines available on the lysine amino acids on the antibodies. A key feature of pHAb Amine Reactive Dye is that it has two sulfonate groups per dye, which increases solubility and reduces the aggregation often seen with other non-sulfonated dyes. pHAb Amine Reactive Dye maintains their fluorescence response to pH change even after antibody conjugation. Even though antibody conjugation is the key application, any protein containing primary amines on lysine amino acids can be conjugated with pHAb Amine Reactive Dye.