Evolution of Fluorescein as a Platform for Finely Tunable Fluorescence Probes

Fluorescence imaging is the most powerful technique currently available for continuous observation of dynamic intracellular processes in living cells. Suitable fluorescence probes are naturally of critical importance for fluorescence imaging, but only a very limited range of biomolecules can currently be visualized because of the lack of flexible design strategies for fluorescence probes. At present, design is largely empirical. Here we show that the carboxylic group of traditional fluorescein dyes, formerly considered indispensable, has been replaced with other substituents, affording various kinds of new fluoresceins. Further, by breaking out of the traditional structure of fluorescein, we developed the…