JC-1 is a novel cationic carbocyanine dye that accumulates in mitochondria. The dye exists as a monomer at low concentrations and yields green fluorescence, similar to fluorescein. At higher concentrations, the dye forms J-aggregates that exhibit a broad excitation spectrum and an emission maximum at ∼590 nm. These characteristics make JC-1 a sensitive marker for mitochondrial membrane potential. Another dye with similar characteristics is JC-9 (D-22421).
Given that JC-1 and JC-9 dyes are mitochondrial membrane potential indicators, they are designed to be used in live cells with active mitochondria. These dyes are not compatible with fixed cell staining.