Ion dependence of CoroNaGreen FL in vitro. Traces shown on the left (A, C, E, and G) represent temporal photon distributions emitted by CoroNaGreen (normalized photon count) after pulsed excitation in different salines as indicated; the insets show an enlargement of the fluorescence intensity decays as a function of time between 0.5–1.2 ns. Graphs on the right (B, D, F, and H) illustrate mean values of τ_AVG ± SD obtained from three experiments each. (A and B) Photon count and τ_AVG of CoroNaGreen in salines with different [Na⁺], ranging from 0–150 mM. Data in B were fit with a sigmoidal function, revealing a K_d of 42.7 mM. In A, the IRF is shown in black. (B) Also depicted is the structural formula of CoroNaGreen as given by the manufacturer. (C and D) Photon count and τ_AVG of CoroNaGreen in salines with a fixed [Na⁺] of 15 mM and potassium concentrations altered between 30 and 150 mM (plotted are 30, 80, 100, 120, and 150 mM). The inset on the left illustrates the nearly complete overlap obtained at 80 and 120 mM [K⁺]. (E and F) pH sensitivity of photon count and τ_AVG of CoroNaGreen at a given [Na⁺] of 20 mM. Plotted are traces obtained at pH 5.0, 5.5, 6.0, 6.5, 7.0, 7.5, and 8.0. (G and H) Photon count and τ_AVG of CoroNaGreen at a [Na⁺] of 20 mM and after addition of dextran at 1, 3, and 5%. Note that addition of dextran did not result in a detectable change in fluorescence intensity decays.