Sterol superlattice affects antioxidant potency and can be used to assess adverse effects of antioxidants.

We have developed a fluorescence method to examine how membrane sterol lateral organization affects the potency of antioxidants, and used this information to evaluate possible adverse effects of lipid-soluble antioxidants seen in recent clinical studies. In the presence of an antioxidant, the lag time (tau) produced during free radical-induced sterol oxidation in lipid vesicles reflects the potency of the antioxidant. The ascorbic acid-induced tau value varies with sterol mol% in a biphasic manner, showing a minimum at the critical sterol mole fraction for maximal superlattice formation (C r), in ascorbic acid concentrations View Article and Find Full Text PDF

Fluorescence detection of signs of sterol superlattice formation in lipid membranes.

There is a significant amount of experimental data, obtained predominantly from fluorescence studies, showing that sterol-containing liposomes can exhibit multiple biphasic changes in membrane properties at specific critical mole fractions of sterol such as 20.0, 22.2, 25.

Fluorometric assay for detection of sterol oxidation in liposomal membranes.

The authors have developed a fluorescence assay to measure the rate and extent of sterol oxidation in lipid bilayers. Dehydroergosterol (DHE), a fluorescent cholesterol analog, is used as a probe and at the same time as a membrane component. The assay can also be performed on bilayers containing a mixture of sterols including DHE and nonfluorescent sterols, such as cholesterol and ergosterol.

Role of sterol superlattice in free radical-induced sterol oxidation in lipid membranes.

We developed a new fluorescence assay for sterol oxidation and used it to study the relationship between free radical-induced sterol oxidation and membrane sterol lateral organization. This assay used dehydroergosterol (DHE) as both a membrane probe and a membrane component. Sterol oxidation was induced by a free radical generator, AAPH (2,2'-azobis(2-amidinopropane)dihydrochloride).

Cholesterol superlattice modulates the activity of cholesterol oxidase in lipid membranes.

Here, the interplay between membrane cholesterol lateral organization and the activity of membrane surface-acting enzymes was addressed using soil bacteria cholesterol oxidase (COD) as a model. Specifically, the effect of the membrane cholesterol mole fraction on the initial rate of cholesterol oxidation catalyzed by COD was investigated at 37 degrees C using cholesterol/1-palmitoyl-2-oleoyl-l-alpha-phosphatidylcholine (POPC) large unilamellar vesicles (LUVs, approximately 800 nm in diameter). In the three concentration ranges examined (18.