JC-1 chloride is a very sensitive fluorescent probe for testing Pgp activity. Capable of distinguishing between resistant, intermediate and sensitve groups, whereas rhodamine 123 only recognizes the resistent group. In cell lines, the red emission band is more convenient for detection of low-level resistance in AML than other probes, such as rhodamine 123 (529nm) or calcein-AM (517nm). Green fluorescent JC-1 existing as a monomer (λem=527nm) at low concentrations or at low membrane potential. However, at higher concentrations (aqueous solutions above 0.1μM) or higher potentials, JC-1 forms red fluorescent ''J-aggregates'', which exhibit a broad excitation spectrum and a very narrow emission spectrum (λem=590nm). JC-1 stains mitochondria in living cells in a membrane potential-dependent funct
