Highly activatable and rapidly releasable caged fluorescein derivatives

Caged fluorophores, which recover fluorescence activity upon brief illumination with ultraviolet (UV) light, have played an important role in investigating cell lineage and cellular protein dynamics. In this paper, we report novel nitrobenzyl-caged fluorescein derivatives, based on our TokyoGreen platform (caged TokyoGreen), which have a single photoremovable protecting group, and the fluorescence quantum efficiency can be finely controlled via the photoinduced electron-transfer process before and after photoactivation. These new derivatives can be activated more rapidly and show a larger fluorescence enhancement than a traditional caged fluorescein, which is a bis-caged lactone form, upon brief UV irradiation both in the biological application and in cuvette experiments.