Fluorescent sensors for a variety of ions, such as Ca2+ and Na+, are among the most useful tools available for studying ion fluxes within the intracellular environment following the modulation or stimulation of a range of complex biological processes. Two widely used fluorescent indicators for Ca2+ ions are Indo-1 (1) and Fura-2 (2), which complex calcium with high affinity (Kd= 230 and 145 nm, respectively), and these reagents have allowed ...