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Cardiolipin binds nonyl acridine orange by aggregating the dye at exposed hydrophobic domains on bilayer surfaces
Author(s) -
Mileykovskaya Eugenia,
Dowhan William,
Birke Ronald L.,
Zheng Donghong,
Lutterodt Lydia,
Haines Thomas H.
Publication year - 2001
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/s0014-5793(01)02948-9
Subject(s) - acridine orange , cardiolipin , chemistry , biophysics , bilayer , biochemistry , membrane , biology , phospholipid , apoptosis
10‐ N ‐Nonyl acridine orange (NAO) has been used at low concentrations as a fluorescent indicator for cardiolipin (CL) in membranes and bilayers. The mechanism of its selective fluorescence in the presence of CL, and not any other phospholipids, is not understood. The dye might recognize CL by its high p K (p K 2 >8.5). To investigate that, we established that NAO does not exhibit a p K in a pH range between 2.3 and 10.0. A second explanation is that the dye aggregates at hydrophobic domains on bilayers exposed by the CL. We found that a similar spectral shift occurs in the absence of CL in a concentrated solution of the dye in methanol and in the solid state. A model is proposed in which the nonyl group inserts in the bilayer at the hydrophobic surface generated by the presence of four chains on the phospholipid.