SPQ is a fluorescent chloride indicator.1 Its fluorescence is rapidly quenched by chloride in vitro. It has been used to assess voltage-sensitive chloride transport in placental microvillus vesicles. It has also been used to continuously quantify intracellular calcium efflux induced by parathyroid hormone, forskolin , and phorbol 12-myristate 13-acetate in isolated human erythrocytes.2 In addition, SPQ has been used to determine the type of ion conductance induced by the cystic fibrosis transmembrane conductance regulator (CFTR) in HEK293 cells expressing pTrial10-CRTR2.3 SPQ displays excitation maxima of 320 and 350 nm and an emission maximum of 445 nm.1
1.Illsley, N.P., and Verkman, A.S.Membrane chloride transport measured using a chloride-sensitive fluorescent probeBiochemistry26(5)1215-1219(1987) 2.Soldati, L., Adamo, D., Spaventa, R., et al.Chloride fluxes activated by parathyroid hormone in human erythrocytesBiochem. Biophys. Res. Commun.269(2)470-473(2000) 3.MacVinish, L.J., Gill, D.R., Hyde, S.C., et al.Chloride secretion in the trachea of null cystic fibrosis mice: the effects of transfection with pTrial10-CFTR2J. Physiol.499(Pt. 3)677-687(1997)