Chloride-Sensitive Fluorescent Indicators

3which is more than twice that of SPQ [6-methoxy-N-(3sulfopropyl)quinolinium] used in recent physiological measurements to measure intracellular chloride levels. The dyes have been characterized using steadystate fluorescence spectroscopy and are compared to three similar dyes based on the 6-methoxyquinoline nucleus, reported earlier by the authors, and also to dyes reported by Krapf et al. (Anal. Biochem. 169, 142‐ 150, 1988). The interference of aqueous anions and the potential for using these dyes in biological halidesensing applications are discussed. © 2001 Academic Press