A very sensitive fluorogenic elastase substrate, Abs/Em=501/527 nm. The colorless and nonfluorescent (Z-Ala-Ala-Ala-Ala)2Rh110 is hydrolyzed to the highly fluorescent Rhodamine 110, which exhibits excellent spectral properties that match the optimal detection window of most fluorescence instruments. After cleavage, Abs(max) is at 497 nm and Em(max) is at 520 nm.