Derivatives of 8-Hydroxy-2-methylquinoline Are Powerful Prototypes for Zinc Sensors in Biological Systems

The recent emphasis on understanding the myriad roles of zinc in both normal and diseased cells and tissues has placed an ever increasing demand on methods for sensitive and selective methods for real-time monitoring of free Zn^(2+) in complex biological samples. Chelation-enhanced fluorescent sensors for zinc, based on fluorophores such as quinoline, dansyl, fluorescein, and anthracene, have been reported. While each of these agents has unique advantages, there remain issues with sensitivity, selectivity, and specificity that may be addressable with an alternate chromophore that is readily amenable to synthetic manipulation. Herein we report the systematic chemical modification of the 8-hydroxy-2-methylquinoline (Oxn) unit as a building block for the development of new sensors employing chelation-enhanced fluorescence. In particular, improvements in quantum yield from 0.004 to 0.70 and stepwise blue shifts in fluorescence emission wavelengths (to a total of over 70 nm) are reported