Patent ID: 7329505

Claim:
A peptide comprising: an amino acid sequence comprising at least a fluorophore and tryptophan for quenching fluorescence emitted from the fluorophore, the fluorophore is not located on said tryptophan; wherein the fluorophore is a fluorescent dye, which when covalently coupled to the peptide emits fluorescence that is quenched by said tryptophan; wherein the fluorescent dye is an oxazine derivative or a rhodamine derivative, which absorbs and emits in a red region of visible light; wherein the fluorophore and said tryptophan are in such spatial proximity that as long as the tryptophan and the amino acid carrying the fluorescent dye have not been separated by an exopeptidase, quenching of the fluorescence of the fluorophore is realized; and wherein after the tryptophan and the amino acid carrying the fluorescent dye are separated by the exopeptidase, an increase in fluorescent emission of the fluorophore is realized.