Patent ID: 6949632

Claim:
A fluorogenic substrate molecule having the following characteristics: (a) said molecule re-emits at least about 70% of the energy of the incident radiation that is used to excite the molecule; (b) the molecule emits radiation at a wavelength that is at least about 25 nm from the wavelength of radiation used to excite the molecule; and (c) the molecule is soluble and stable in water; wherein said molecule has the following structure: and salts thereof, wherein: R 1 is selected from the group consisting of phospate, —OH, sulfonamide, and substrates for hydrolytic enzymes; and R 2 , R 3 , and R 4 are, independently, selected from the group consisting of SO 3 , NR 5 R 6 , SO 2 NR 5 R 6 , and halides; wherein R 5 and R 6 are, independently, selected from the group consisting of H, and C 1-6 ; provided that at least one of R 2 , R 3 , or R 4 is a halide.