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 an effective compound for confocal laser scanning microscopy, characterized by its excitation at 490 nm and fluorescence emission around 510 nm. Its fluorescence intensity correlates positively with magnesium ([Mg]) concentration, while remaining inert to sodium, potassium, and calcium ions. This specificity is evidenced by a dissociation constant (Kd) for Mg at 3 mM, indicating its proficiency in exclusively tracking [Mg] changes under physiological conditions. In experimental setups, PC12 cells infused with KMG-104 and the calcium indicator fura-2 have facilitated the exploration of intracellular magnesium in cellular components such as endoplasmic reticulums (ERs), mitochondria, and Mg-ATP complexes.