TSQ, q.v., derived membrane permeant fluorescent probe selective for Zn2+ in the presence of Ca2+ and Mg2+. Synthesis: I. B. Mahadevan et al., Aust. J. Chem. 49, 561 (1996). Coordination chemistry: C. J. Fahrni, T. V. O'Halloran, J. Am. Chem. Soc. 121, 11448 (1999); potentiometric coordination of fluorophore: K. M. Hendrickson et al., ibid. 125, 3889 (2003). Visualization of intracellular Zn2+ pools in pancreatic islets: P. D. Zalewski et al., J. Histochem. Cytochem. 42, 877 (1994); in apoptosis: P. J. Smith et al., Am. J. Physiol. Cell Physiol. 283, C609 (2002); G. R. Sauer et al., J. Cell. Biochem. 88, 954 (2003).