JC-1 is a membrane permeable dye widely used for determining mitochondrial membrane potential in flow cytometry and fluorescent microscopy. This dye can selectively enter the mitochondria where it reversibly changes color as membrane potentials increase (over values of about 80-100 mV). This property is due to the reversible formation of JC-1 aggregates upon membrane polarization that causes shifts in emitted light from 530 nm (i.e., emission of JC-1 monomeric form) to 590 nm (i.e., emission of J-aggregate) when excited at 488 nm. Both colors can be detected using filters for FITC and PE/phycoerythrin/rhodamine, respectively. JC-1 is both qualitative, in regards to the shift from green to orange fluorescence emission, and quantitative, as measured by fluorescence intensity, in both filter sets. JC-1 can be used to indicate the initiation of apoptosis. Molecular Weight: 652.23 Peak Excitation: 515 nm Peak Emission: 529 and 590nm JC-1 should be reconstituted in high quality freshly opened DMSO at 1mg/ml. Once reconstituted, it should be stored at -20°C avoid freeze-thawing.