Characteristics of commonly used FRET fluorophores in main protease assays reported in the literaturea.
| Fluorophore | Ex (nm) | Em (nm) | R o (Förster, nm) | Φ FL (buffered) water, pH 7–7.4 | Typical quencher |
|---|---|---|---|---|---|
| AMC, 7-amino-4-methylcoumarin | 351 | 431 | 0.86 (ref. 10) | — | |
| MCA, 7-methoxycoumarin-4-acetic acid | 325 | 420 | 3.7 (ref. 10) | 0.72 (ref. 10) | Dnp (2,4-dinitrophenyl) |
| 2-Abz, 2-aminobenzoic acid | 320 | 420 | 3.1 (ref. 11) | 0.64 (ref. 12) | Y(NO2) (3-nitrotyrosine) |
| EDANS, 5-(2-aminoethylamino)-1-naphthalenesulfonic acid | 340 | 490 | 3.3 (ref. 13) | 0.27 (ref. 14) | Dabcyl (4-(4-dimethylaminophenylazo)benzoyl) |
| FAM, 5-carboxyfluorescein | 492 | 518 | ∼4.9 (ref. 15) | 0.83 (ref. 16) | Dabcyl (4-(4-dimethylaminophenylazo)benzoyl) |
a
Abbreviations: ΦFL, fluorescence quantum yield.