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H Wennerström

Publications and source records attributed to H Wennerström.

22 records · Page 2Linked to original sources
PubMed1977

Amphiphile diffusion in model membrane systems studied by pulsed NMR.

The translational diffusion of the amphiphilic molecules in a number of lyotropic liquid crystalline phases has been measured with the pulsed NMR pulsed magnetic field gradient method. The amphiphiles studied were soaps, monoglycerids and lecithins. Measurements were performed both for oriented lamellar and for cubic phases. The order of magnitude of the diffusion coefficients was found to be the same as in neat liquids of analogous compounds. It was also found that the difussion coefficient depend markedly on the amphiphile end group in a way that parallels the area per polar head group as determined in X-ray studies. When corrections for geometrical factors has been made the diffusion rate is approximately equal in cubic and lamellar phases containing the same amphiphile.

Chemical Phenomena↗
PubMed1976

Lecithin translational diffusion studied by pulsed nuclear magnetic resonance.

The translational diffusion coefficient of egg yolk and dilauroyl lecithin in optically isotropic phases containing sodium cholate has been measured using the pulsed NMR magnetic field gradient method. After a correction for geometrical factors the measured diffusion coefficient is found to agree well with previous determinations in phospholipid systems. The experimental data imply that the cubic mesophase of the lecithin-sodium cholate-water system contains continuous lipid aggregates. A possible model of the arrangement of the different amphiphile molecules in the cubic phase is discussed.

Diffusion↗
PubMed1975

Proton NMR bandshape studies of lamellar liquid crystals and gel phases containing lecithins and cholesterol.

Proton NMR spectra for gel and liquid crystalline samples, composed of dimyristoyl and/or dipalmitoyl lecithin, cholesterol and water, can be consistently interpreted in terms of mesophase symmetry and molecular diffusion according to a model proposed by Wennerstrom (Wennerstrom, H. (1973) Chem. Phys. Lett. 18, 41-44). It is shown by computer simulation that the characteristic "super-lorentzian" bandshape of the lamellar mesophase can be described by the superposition of three gaussian curves. The NMR signal of the gel phase can be simulated by the superposition of two gaussian curves with widths at half height of 2.5 kHz and 19 kHz. An upper limit of the lateral diffusion coefficient of the lecithin molecules in the gel phase is calculated to be about 5-10(-15) m-2/s. It is therefore concluded that the static intermolecular dipolar couplings average to zero in the lamellar mesophase. An estimation of the order parameter of the liquid crystalline phase is made from experimental data and a calculated "rigid lattice" linewidth. A two phase system is shown to exist in the temperature range 28-34 degrees C for a mesophase of a mixture of dimyristoyl and dipalmitoyl lecithin. The presence of cholesterol results in enhanced lateral diffusion of the lecithin molecules at temperatures below the Chapman transition point.

Binding Sites↗