Mitochondrial membrane potential
DETECTION OF CHANGES IN MITOCHONDRIAL MEMBANE POTENTIAL
Proper mitochondrial function requires a negative charge on the inner side of the mitochondrial inner membrane. A potential difference is maintained by the asymmetrical distribution of H+ ions across the membrane. Cationic lipophilic dyes such as JC-1, TMRE (tetramethylrhodamine ethyl ester), DiOC6(3), DiIC1(5), CMXRos (MitoTracker Red), LDS-751 and rhodamine 123 localize across the inner mitochondrial membrane. Loss of membrane potential is detected in cells by measuring a loss of dye from the inner mitochondrial matrix or a change in fluorescence of the dye as the transmembrane potential drops.
JC-1 is a cationic carbocyanine dye that accumulates in mitochondria. The dye exists as a monomer at low concentrations (e.g. in the cytoplasm) and emits green fluorescence, similar to fluorescein. At higher concentrations (obtained in mitochondria), the dye forms J-aggregates that exhibit an emission maximum at ~590 nm (orange). When mitochondrial membrane potential is lost JC-1 shows an emission change (orange to green).
The drop in TMRE accumulation in cells during the process of apoptosis is presented in the Apoptosis section.