Extraction of lipid membrane incorporated vitamin E by sucrose polyesters.

2H and 31P solid state NMR have been used to probe, at the molecular level, the interaction between structurally different sucrose polyesters and a phospholipid membrane into which alpha-tocopherol and specifically deuterated alpha-[5,7-(2)H(6)] tocopherol has been incorporated. Our results show that at high concentration (>or=10 mol%) sucrose octapalmitate (SOP) and sucrose hexapalmitate (SHxP) deplete bilayer-associated alpha-tocopherol in dipalmitoyl phosphatidalcholine (DPPC) multilamellar dispersions and preferentially sequester the alpha-tocopherol into a fluid sucrose polyesters (SPE) phase located proximal to the membrane surface. It is demonstrated that the ability of SPEs to function as a 'lipophilic sink' depends strongly on sucrose polyester concentration and degree of esterification.

Membrane perturbing properties of sucrose polyesters.

Sucrose polyester (SPE), in the form of sucrose octaesters and sucrose hexaesters of palmitic (16:0), stearic (18:0), oleic (18:1cis), and linoleic (18:2cis) acids, have many uses. Applications include: a non-caloric fat substitute, detoxification agent, and oral contrast agent for human abdominal (MRI) magnetic resonance imaging. However, it has been shown that the ingestion of SPE was shown to generate a depletion of physiologically important lipidic vitamins and other lipophilic molecules. In order to better understand, at the molecular level, the type of interaction between SPE and lipid membrane, we have, first synthesized different type of labelled and non-labelled SPEs. Secondly, we have studied the effect of SPEs on multilamellar dispersions of dielaidoylphosphatidylethanolamine (DEPE) and dipalmitoylphosphocholine (DPPC) as a function of temperature, SPE composition and concentration. The effects of SPEs were studied by differential scanning calorimetry (DSC), X-ray diffraction, 2H and 31P NMR spectroscopy. At low concentration (< 1 mol%) all of the SPEs lowered the bilayer to the inverted hexagonal phase transition temperature of DEPE and induced the formation of a cubic 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 31P NMR. Order parameter measurements of DPPC-d62/SPE mixtures show that the SPE effect on the DPPC monolayer thickness is dependent on the SPE, concentration, chains length and saturation level. At higher concentration (> or = 10 mol%) SPE are very potent DEPE bilayer to HII phase transition promoters, although at that concentration the SPE have lost the ability to form cubic phases. SPEs have profound effects on the phase behaviour of model membrane systems, and may be important to consider when developing current and potential industrial and medical applications.

Solid state 13C NMR of 30-crown-10 ether and 30-crown-10.4H2O.

The 13C NMR solution spectra of 30-crown-10 ether and its tetrahydrate show only one resonance at all accessible temperatures. In contrast, the solid state 13C NMR spectrum of the 30-crown-10.4H2O shows two resonances in the ratio of 4:1, separated by 1.2 ppm. In the case of 30-crown-10 itself, six resolvable 13C resonances in the ratio of 4:1:1:2:1:1 are observed in the solid with an overall chemical shift dispersion of 5 ppm. The remarkably different spectral behavior of these two systems in the solid state is discussed in terms of the torsional environments of the crystallographically unique carbons and the results of GIAO calculations of isotropic 13C shieldings for simpler model compounds. Results of dipolar dephased 13C CPMAS spectra indicate that 30-crown-10 does not undergo a large amplitude molecular motion, in contrast to earlier results for 18-crown-6. Only a small amount of residual intensity is found in the dipolar dephased spectrum of 30-crown-10.4H2O, indicating that it also is relatively rigid in the solid.

Solid state molecular motion in sucrose octapalmitate as studied by deuterium NMR spectroscopy.

Sucrose octapalmitate-d11, d24 and d248 have been synthesized. Using 2H NMR T1 and analyses of the temperature dependence of the lineshapes, a detailed description of the solid state molecular motional modes is presented. Activation energies for methyl and methylene group rotation in the fatty acyl chains have been determined. The sucrose moiety is found to be static on the solid state deuterium NMR timescale.

Application of proton and 13C-NMR spectroscopy to estimation of diastereoisomer ratio in phenethicillin.

A procedure for the determination of the diastereoisomer ratio in phenethicillin potassium and its formulations is described. The method utilizes analyses of PMR and 13C-NMR data. Assignments of 13C-chemical shifts in D- and L-phenethicillin potassium also are included.