Magic angle spinning 13C-NMR spin-lattice relaxation study of the location and effects of ?-tocopherol, ubiquinone-10 and ubiquinol-10 in unsonicated model membranes

Abstract

Abstract. e-Tocopherol, ubiquinone-10 and ubiquinol-10 have been studied by high resolution magic angle samples spinning 13C-nuclear magnetic resonance in egg yolk phosphatidylcholine multilamellar vesicles model membranes in order to assess their location and the induced perturbations on this model system. ~-Tocopherol is placed in such a position that it is in close contact with the head group of the phospholipid and exposed to the solvent. In this position it significantly perturbs the phospholipid head group, the 5a-CH 3 and the 7a-CH 3 groups being the closest parts to the membrane surface. On the other hand, ubiquinol-10 perturbs the membrane surface more than ubiquinone-10, but neither compound significantly changed the phospholipid head group conformation.

Location of Cholesterol in Model Membranes by Magic‐Angle‐Sample‐Spinning NMR

“…Therefore, the (TIM)-' values obtained for the different carbons in the PtdCho/cholesterol mixture should allow us to obtain relative distances to the phosphate group where the Gd3' is bound. Significantly, upon inclusion of cholesterol in PtdCho and in the presence of Gd", there were no PtdCho resonances broadened beyond detection, as was the case when a-tocopherol was inserted into model membranes (Salgado et al, 1993). In the last case, it was the result of the perturbation of the phospholipid induced by the presence of a-tocopherol in the upper part of the palisade structure of the bilayer.…”

“…2). It is also interesting to compare the phospholipid nT, values in the presence of cholesterol with those obtained in the presence of a-tocopherol and coenzyme Q, both in the oxidized and in the reduced forms (Salgado et al, 1993). It was found that a-tocopherol ordered the head group and the acyl chain of the phospholipid, whereas the molecule of coenzyme Q, in its two forms, slightly disordered the acyl chain of the phospholipid.…”

“…At the same time, X-ray crystallography is hampered by the fact that the system is far from being in its natural hydrated state. Recent work using solid-state NMR instrumentation has permitted the obtaining of very-high-resolution NMR spectra of multilamellar model and natural membrane systems, which has opened the way to obtain direct information on membrane structure and dynamics, and it has made it possible to determine specific properties of lipids and peptides incorporated into the phospholipid lamellar phase (Abebodun et al, 1992;Bouchard et al, 1995;Davies et al, 1995;Forbes et al, 1988a, b;Guo and Hamilton, 1995;Hamilton et al, 1991;Oldfield et al, 1987;Salgado et al, 1993). In this work we aimed to exactly localize the molecule of cholesterol when incorporated into well-hydrated non-perturbed phospholipid multilamellar vesicles by using MAS-NMR.…”

“…Nevertheless, very useful information about molecular motions and conformations of phospholipidcholesterol mixtures has been obtained on phospholipid multilayer dispersions studied by using solid-state 'H-NMR and "C-NMR (Dufourc et al, 1984;Hamilton et al, 1993;Huang et al, 1993;Murari et al, 1986;Oldfield et al, 1978;Taylor et al, 1981;Vist and Davis, 1990). The technique of magic-angle-sample-spinning (MAS) NMR can potentially eliminate the line-broadening in spectra of orderedlanisotropic systems and yields high-resolution spectra from which chemical shift and relaxation measurements can be made (Forbes et al, 1988a, b ;Oldfield et al, 1987;Salgado et al, 1993;Sefcik et al, 1983).…”

The location and behavior of α‐tocopherol in membranes

“…Both molecules are anchored at the aqueous interface by an OH group [11,30,31] have rigid rings at mid-structure and a branched chain protruding into the membrane interior. Admittedly, the amount of a-tocopherol in membranes is usually considerably less than cholesterol (such as in plasma membranes), but perhaps not in others, such as in the late endosome/lysosome [32,33].…”