“…A popular approach to biosensor design is the conjugation of a fluorescent group to a solute-binding protein that harbors specificity for the target molecule, exploiting ligand-induced fluorescence changes in the protein–fluorophore conjugate to detect a target [ 1 , 2 ]. These protein-based biosensors have been utilized for amino acid detection [ 3 , 4 , 5 , 6 ], anion or cation detection [ 4 , 7 , 8 , 9 , 10 ], nucleotide detection [ 11 , 12 , 13 ], and carbohydrate detection [ 4 , 14 , 15 , 16 , 17 , 18 , 19 ]. Protein-based biosensors are often constructed by placing a fluorescent group in close proximity to the ligand-binding site, exploiting ligand-binding events to change the local environment probed by the fluorescent group.…”