JC-1 is a mitochondrial dye that stains mitochondria in living cells in a membrane potential-dependent fashion. JC-1 monomer is in equilibrium with so called J-aggregates, which are favored at higher mitochondrial membrane potential. The monomer JC-1 has green fluorescence (lem = 527 nm), while the J-aggregates have red fluorescence (lem = 590 nm). Therefore, it has been possible to use fluorescence ratioing technique to study mitochondrial membrane potential. JC-1 is particularly useful for apoptosis studies. In apoptotic cells, the dye stays in the cytoplasm and fluoresces green, while in healthy cells, the dye aggregates in the mitochondria and fluoresces red. MW: 652.23. Purity >98% by HPLC