title: Gel-phase microdomains and lipid rafts in monolayers affect the redox properties of ubiquinone-10.
abstract: The redox properties of ubiquinone-10 (UQ) were examined in monolayers of mixtures of dioleoylphosphatidylcholine, palmitoylsphingomyelin, and cholesterol of different compositions, self-assembled on a mercury electrode, over the pH range from 7.5 to 9.5. A detailed analysis of the cyclic voltammograms of UQ in the above lipid environments points to a mechanism consisting of an elementary electron transfer step followed by two protonation (or deprotonation) steps in quasiequilibrium and by a further electron transfer step. In a lipid environment of solid-ordered (s(o)) microdomains in a liquid-disordered (l(d)) matrix, electron transport across the lipid monolayer takes place in the l(d) phase. In a pure s(o) phase, UQ tends to segregate into UQ-rich pools, exhibiting reversible electron transfer steps. In a lipid environment consisting of liquid-ordered (l(o)) microdomains (lipid rafts) in an l(d) matrix, UQ molecules tend to localize along the edge of the lipid rafts. However, in a lipid environment consisting exclusively of l(o) and s(o) microdomains, UQ molecules tend to segregate into UQ-rich pools. In all lipid environments, electron transport by UQ occurs with the quinone moiety localized on the solution side with respect to the ester linkages of the dioleoylphosphatidylcholine molecules.
authors: Chemistry Department, Florence University, Firenze, Italy.
authors: Lucia
authors: L
authors: Becucci
authors: Federica
authors: F
authors: Scaletti
authors: Rolando
authors: R
authors: Guidelli
mesh_terms: D002784:Cholesterol / Q000737:chemistry; D055664:Electrochemical Techniques; D005782:Gels; D006859:Hydrogen / Q000737:chemistry; D007700:Kinetics; D021962:Membrane Microdomains / Q000737:chemistry*; D008628:Mercury / Q000737:chemistry; D010084:Oxidation-Reduction; D010713:Phosphatidylcholines / Q000737:chemistry; D013109:Sphingomyelins / Q000737:chemistry; D013816:Thermodynamics; D014451:Ubiquinone / Q000737:chemistry*
chemical_list: D005782:Gels; D010713:Phosphatidylcholines; D013109:Sphingomyelins; C033171:palmitoylsphingomyelin; D014451:Ubiquinone; D006859:Hydrogen; D002784:Cholesterol; C017251:1,2-oleoylphosphatidylcholine; D008628:Mercury; C025204:Ubiquinone Q2