title: Fluorescence studies of the interactions of ubiquinol-10 with liposomes.
abstract: Ubiquinone-10 plays a central role in energy production and its reduced form, ubiquinol-10 is also capable of acting as a potent radical scavenging antioxidant against membrane lipid peroxidation. Efficiency of this protection depends mostly on its localization in lipid bilayer. The intrinsic fluorescence of ubiquinol-10 and of the exogenous probe, Laurdan, has been used to determine the location of ubiquinol-10 in unilamellar liposomes of egg phosphatidylcholine (EggPC) and dimyristoyl phosphatidylcholine. Laurdan fluorescence moiety is positioned at the hydrophilic-hydrophobic interface of the phospholipid bilayer and its parameters reflect the membrane polarity and microheterogeneity, which we have used to explore the coexistence of microdomains with distinct physical properties. In liquid-crystalline bilayers ubiquinol has a short fluorescence lifetime (0.4 ns) and a high steady-state anisotropy. In a concentration-dependent manner, ubiquinol-10 influences the Laurdan excitation, emission and generalized polarization measurements. In EggPC liposomes ubiquinol-10 induces a decrease in membrane water mobility near the probe, while in dimyristoyl liposomes a decrease in the membrane water content was found. Moreover the presence of ubiquinol results in the formation of coexisting phospholipid domains of gel and liquid-crystalline phases. The results indicate that ubiquinol-10 molecules are mainly located at the polar-lipid interface, inducing changes in the physico-chemical properties of the bilayer microenvironment.
authors.affiliation: Biochemistry Institute, Marche Polytechnic University, Ancona, Italy. rfiorini2003@yahoo.it
authors.forename: Rosamaria
authors.initials: R
authors.lastname: Fiorini
authors.forename: Letizia
authors.initials: L
authors.lastname: Ragni
authors.forename: Simona
authors.initials: S
authors.lastname: Ambrosi
authors.forename: Gian Paolo
authors.initials: GP
authors.lastname: Littarru
authors.forename: Enrico
authors.initials: E
authors.lastname: Gratton
authors.forename: Theodore
authors.initials: T
authors.lastname: Hazlett
mesh_terms: D015081:2-Naphthylamine / Q000031:analogs & derivatives / Q000737:chemistry; D007848:Laurates / Q000737:chemistry; D008081:Liposomes / Q000737:chemistry; D015394:Molecular Structure; D013050:Spectrometry, Fluorescence; D013816:Thermodynamics; D014451:Ubiquinone / Q000031:analogs & derivatives* / Q000737:chemistry
chemical_list: D007848:Laurates; D008081:Liposomes; D014451:Ubiquinone; C026663:ubiquinol-10; D015081:2-Naphthylamine; C065580:laurdan