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A ²H-NMR study of the comparative effects of lanosterol and cholesterol on model membranes Wallace, Julia C.


Suspensions of sn-2 deuterated ²H-DPPC-d31 containing various concentrations of either lanosterol or cholesterol were compared using deuterium nuclear magnetic resonance spectroscopy (²H-NMR) and differential scanning calorimetry (DSC). The alpha face of cholesterol is smooth whereas a hydroxyl group protrudes from the alpha face of lanosterol. At the sterol concentrations studied, (0%, 5%, 10%, 15%), the phase behaviour of lanosterol and cholesterol was similar. M, profiles showed that the gel to liquid crystalline phase transition is broadened with the incorporation of both sterols and that mixed phase regions exist at comparable concentrations and temperatures. Both lanosterol and cholesterol increase the average order of the phospholipids above the transition temperature. Since both lanosterol and cholesterol produce this ordering, it is proposed that the significant structural feature producing this result is the rigidity of the cholestane ring. T[sub 2e] increases with the incorporation of both cholesterol and lanosterol. This could indicate the importance of the rigid ring structure which may modify slow motions such as the collective motions of the phospholipid chains.

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