Fluorescent Ca2+ indicator (Kd for Ca2+ = 250 nM). Cell-permeable. Displays ratiometric emission wavelength change upon Ca2+ binding. Excitation/emission λ are 355/475 nm for no Ca2+ and 355/401 nm for high Ca2+. Absorption maxima are 349 and 331 nm for free anion and Ca complex, respectively. Respective emission maxima are 485 and 410 nm. Quantum yield ~0.5. Ideal for flow cytometry. Purity 90%. MW (observed): 1009.91