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10 N ‐Nonyl acridine orange interacts with cardiolipin and allows the quantification of this phospholipid in isolated mitochondria

1992; Wiley; Volume: 209; Issue: 1 Linguagem: Inglês

10.1111/j.1432-1033.1992.tb17285.x

1432-1033

Jean‐Michel Petit, Abderrahman Maftah, Marie‐Hélène Ratinaud, Raymond Julien,

ATP Synthase and ATPases Research

The acridine orange derivative, 10 N ‐nonyl acridine orange, is an appropriate marker of the inner mitochondrial membrane in whole cells. We use membrane model systems to demonstrate that 10 N ‐nonyl acridine orange binds to negatively charged phospholipids (cardiolipin, phosphatidylinositol and phosphatidylserine). The stoichiometry has been found to be 2 mol 10 N ‐nonyl acridine orange/mol cardiolipin and 1 mol dye/mol phosphatidylserine or phosphatidylinositol, while, with zwitterionic phospholipids, significant binding could not be detected. The affinity constants were 2 × 10 6 M −1 for cardiolipin‐10 N ‐nonyl‐acridine‐orange association and only 7 × 10 4 M −1 for that of phosphatidylserine and phosphatidylinositol association. The high affinity of the dye for cardiolipin may be explained by two essential interactions; firstly an electrostatic interaction between the quaternary ammonium of nonyl acridine orange and the ionized phosphate residues of cardiolipin and secondly, hydrophobic interactions between adjacent chromophores. A linear relationship was demonstrated between the cardiolipin content of model membranes and the incorporated dye. Consequently, a convenient and rapid method for cardiolipin quantification in membranes was established and applied to the cardiolipin‐containing organelle, the mitochondrion.