In this protease substrate, collagen is heavily labeled with a fluorescein derivative, resulting in almost total quenching of the conjugate's fluorescence. Protease-catalyzed hydrolysis relieves this quenching conjugate, yielding brightly green fluorescent dye-labeled peptides. The increase in fluorescence intensity is directly proportional to protease activity. Collagen, Type IV should be particularly useful in the development of HTS assays for screening Gelatinase A (MMP-2) and Gelatinase A inhibitors, as well as for other gelatinases and collagenases that specifically degrade (Type IV) Collagen. Additionally, lightly fluorescein-labeled collagen may be useful for continuous assays monitored by fluorescence polarization.