Mag-Fura-2 AM, a cell-permeable fluorescent compound, serves as a selective indicator for magnesium ions (Mg2+), demonstrating significant preference for Mg2+ over other bivalent ions including zinc (Zn2+), copper (Cu2+), and calcium (Ca2+). It notably exhibits over 13,000-fold greater selectivity for Mg2+ compared to Ca2+ (Mg2+Kd = 1.9 nM vs. Ca2+Kd = 25 μM). The excitation and emission peak wavelengths are 369 nm and 511 nm, respectively. Further, Mag-Fura-2 AM is utilized as an indirect measure of ATP consumption or production due to its magnesium ion sensitivity.