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Fluorescence quenching of lipid-boundpyrene was used to assessthe binding of cytochrome c(cyt c) to liposomes that mimic the inner mitochondrial membrane (IMM)POPC/DOPE/TOCL, with the conditions that it did ordid not contain oxidized phosphatidylcholine molecules, i.e.,1-O-hexadecyl-2-azelaoyl-sn-glycero-3-phosphocholine(PazePC), or a mixture of two hydroperoxide isomers derivedfrom POPC (POPCOX). The binding isotherms reveal two dissociationconstants, KD1and KD2, representing, respectively, thelow- and high-affinity states of the membrane. These dissociationconstants probably are due to the lipid reorganization promoted bycyt c, as observed in giant unilamellar vesiclesthat contain fluorescent cardiolipin (CL). The presence of PazePC,which has a nonreactive carboxylic group, increased the KD1and KD2values 1.2- and 4.5-fold, respectively. The presence of POPCOXwhich has a reactive peroxide group, decreased the KD1value 1.5-fold, increased the KD2value 10-fold, and significantlyreduced the salt-induced detachment of cyt c. MALDI-TOF spectrometry analysis of cyt cincubatedwith liposomes containing POPCox demonstrated a mass increase correspondingto the formation of nonenal adducts as hydrophobic anchors. Electronicabsorption spectroscopy, circular dichroism, and magnetic circulardichroism demonstrated that all of the lipids studied promoted changesin the cyt ccoordination sphere. Therefore,in the presence of CL, the oxidation of zwitterionic lipids also promoteschanges in the cyt cstructure and in the affinityfor lipid bilayers. [ABSTRACT FROM AUTHOR]