Solvation Dynamics of a Probe Covalently Bound to a Protein and in an AOT Microemulsion:  4-(N-Bromoacetylamino)-Phthalimide

4-( N -bromoacetylamino)-phthalimide ( I ) is used as a new solvation probe for protein and microemulsions. The photophysics of the probe 4-( N -bromoacetylamino)-phthalimide ( I ) is dramatically different from that of the parent compound, 4-aminophthalimide (4-AP). The solvation dynamics of I in an AOT microemulsion is similar to that of 4-AP in microemulsions. Solvation dynamics in the vicinity of a protein glutaminyl-tRNA synthetase (GlnRS) is studied by covalently attaching I to the protein. The solvation dynamics of the protein-bound probe is described by a very fast component of 40 ps and another of 580 ps.