This substrate has a fluorescent Trp residue in subsite P?2 and a dinitrophenol (Dnp) quenching group at the N-terminus. The quenching of the Trp fluorescence in the intact substrate is relieved upon hydrolysis of the P1-P?1 bond, giving rise to a continuously recording fluorescence assay. The residues placed in subsites P3-P?1 and P?3 is optimized for MMP-8, while Arg is placed in P?4 to enhance solubility.