The carboxylic acid of 7-methoxycoumarin-3-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 blue-fluorescent bioconjugates with absorption/emission maxima ~336/402 nm.