The decrease of mitochondrial membrane potential is a marker event in the early stage of apoptosis. It occurs before the appearance of nuclear apoptotic features (chromatin condensation and DNA fragmentation). Once the mitochondrial membrane potential collapses, apoptosis is irreversible.\nJC-1 is an ideal fluorescent probe widely used to detect mitochondrial membrane potential ∆Ψm. In normal cells, the mitochondrial membrane potential is high, JC-1 aggregates in the mitochondrial matrix to form a polymer, which can produce red fluorescence. In the early stage of apoptosis, the mitochondrial membrane potential decreases, JC-1 can’t accumulate in the mitochondrial matrix. When JC-1 is a monomer, it can produce green fluorescence.\nThe decrease of cell membrane potential can be detected by the transition of JC-1 from red fluorescence to green fluorescence, and the transition of JC-1 fluorescence color can be used as an early detection indicator of cell apoptosis. The relative ratio of red and green fluorescence is commonly used to measure the ratio of mitochondrial depolarization.\nThe maximum excitation wavelength of JC-1 monomer is 514 nm and the maximum emission wavelength is 529 nm; the maximum excitation wavelength of JC-1 polymer is 585 nm and the maximum emission wavelength is 590 nm
