Membrane perturbing properties of sucrose polyesters

Sucrose polyester (SPE), in the form of sucrose octaesters and sucrose hexa esters of palmitic (16.0), stearic (18.0). oleic (18:1(cis)), and linoleic (18:2cis) acids, have many uses. Applications include: a non-caloric fat su bstitute. detoxification agent, and oral contrast agent for human abdominal (MRI) magnetic resonance imaging. However, it has been shown that the inge stion of SPE was shown to generate a depletion of physiologically important lipidic vitamins and other lipophilic molecules. In order to better unders tand, at the molecular level, the type of interaction between SPE and lipid membrane, we have, first synthesized different type of labelled and non-la belled SPEs. Secondly, we have studied the effect of SPEs on multilamellar dispersions of dielaidoylphosyhatidylethanolamine (DEPE) and dipalmitoylpho sphocholine (DPPC) as a function of temperature, SPE composition and concen tration. The effects of SPEs were studied by differential scanning calorime try (DSC), X-ray diffraction,H-2 and P-31 NMR spectroscopy. At low concentr ation ( < 1 mol%) all of the SPEs lowered the bilayer to the inverted hexag onal phase transition temperature of DEPE and induced the formation of a cu bic phase in a composition dependent manner. At the same low concentration, SPEs in DPPC induce the formation of a non-bilayer phase as seen by P-31 N MR. Order parameter measurements of DPPC-d62/SPE mixtures show that the SPE effect on the DPPC monolayer thickness is dependent on the SPE, concentrat ion, chains length and saturation level. At higher concentration (<greater than or equal to> 10 mol%) SPE are very potent DEPE bilayer to H-II phase t ransition promoters, although at that concentration the SPE have lost the a bility to form cubic phases. SPEs have profound effects on the phase behavi our of model membrane systems, and may be important to consider when develo ping current and potential industrial and medical applications. (C) 2001 El sevier science Ireland Ltd. All rights reserved.