The carboxylic acid of Oregon Green® 488 carboxylic acid can be activated in an aqueous solution with a water-soluble carbodiimide such as EDAC (E2247) in order to couple this fluorophore to amines, hydrazines or hydroxylamines on biomolecules of interest to create green-fluorescent bioconjugates with excitation/emission maxima ~492/518 nm. This fluorinated analog of fluorescein overcomes some of the key limitations of fluorescein, including greater photostability and a lower pK_a (pK_a ~ 4.7 versus 6.4 for fluorescein), making its fluorescence essentially pH insensitive in the physiological pH range.