KMG-104 is a fluorescent magnesium (Mg2+) probe known for its exceptional selectivity. It has been extensively utilized to investigate the mobilization of Mg2+ in the cytoplasm across different cell types.

KMG-104 is useful for confocal laser scanning microscopy because it is excited at 490 nm, and emitted fluorescence around 510 nm. Fluorescent intensity of KMG-104 increases with [Mg] increase, and it shows no response to Na, K, and Ca; the dissociation constant (K d ) for Mg is 3 mM. KMG-104 is able to trace only [Mg] change inphysiological conditions[2]. PC12 cells are loaded with a novel Mg indicator KMG-104 and Ca indicator fura-2, and intracellular Mg is studied in the endoplasmic reticulums (ERs), mitochondria, and Mg-ATP[2].