Carbonylcyanide-2-nitro-4-azidophenylhydrazone (an Azido Derivative of the Mitochondrial Uncoupler CCCP) As a Photosensitive Protonophore

An azido derivative of the mitochondrial uncoupler carbonyl cyanide-m-chlorophenylhydrazone (CCCP), namely carbonyl cyanide-2-nitro-4-azidophenyl hydrazone (N3 CCP), has previously been used to study the binding sites of uncouplers on mitochondrial proteins. In this study, we compared the protonophoric activity of N3 CCP and CCCP on an artificial bilayer lipid membrane (BLM) and the uncoupling activity of these compounds in isolated rat liver mitochondria. Both compounds induced electrical current through the BLM at micromolar concentrations and uncoupled mitochondria at submicromolar concentrations. Both protonophoric and uncoupling activities of N3 CCP were effectively inhibited by UV light, whereas CCCP was light-insensitive. These results indicate that N3 CCP is modified by UV light to form products incapable of hydrogen ion transport across artificial or natural membranes.