Effect of Cholesterol and Diacylglycerols

The influence of cholesterol concentration at various temperatures on the thermotropic phase behavior and organization of saturated PE bilayers has been studied by combining DSC, FT-IR, and 31P-NMR. It was found that incorporation of low levels of cholesterol into the bilayer caused a progressive reduction in the temperature, enthalpy, and overall cooperativity of the lipid hydrocarbon chain melting transition 

The influence of the amount of cholesterol at various temperatures on the thermotropic phase behavior and organization of saturated phosphatidylethanolamine bilayers has been 

The interaction of saturated diacylglycerols (DAGs) with phospholipid bilayers has been examined by various NMR techniques [71], [72], [73] and complementary techniques such as DSC and X-ray dif action have been used as well [74]. It has been shown that DAGs induce a decrease in the area per phospholipid molecule and cause a parallel increase in lateral surface pressure of the bilayer. 

This is of interest because the effect of such additives on the rate of membrane fusion in model systems often correlates with the effect of these additives on the bilayer-to-hexagonal phase transition temperature [75]. The increase in the bilayer-to-Hn-phase transition temperature generally inhibits cell fusion, and several compounds which stabilize bilayers show antiviral activity [76]. 

Most of the examples published deal with the interaction of anesthetics with membranes, but calcium channel openers, P-blockers, antimalarials, anticancer drugs and antibiotics have also been examined, and the NMR signals of atoms and groups of the lipid and of the drug molecules have been followed and described as a function of the interaction. For the interaction of anesthetics and the involved mechanism of action, the reader s attention is directed to a review [45]. 

1 P-NMR to Study Changes in Orientation of Phospholipid Head Groups 

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