Bacterial Sortase Substrate III, Abz/DNP TFA is an internally quenched fluorescent peptide used to monitor the activity of the Staphylococcus aureus transpeptidase sortase A (SrtA). This enzyme catalyzes the formation of an amide bond between the carboxyl group of threonine and the amino group of cell-wall crossbridges by cleaving its native substrate, Bacterial Sortase Substrate III, Abz/DNP. The cleavage event can be detected with excitation/emission wavelengths of Ex/Em=320 nm/420 nm.