Estimation of the location of natural \u3b1-tocopherol in lipid bilayers by 13C-NMR spectroscopy

Natural, 2R,4\u2032R,8\u2032R-\u3b1-tocopherol (vitamin E), labelled selectively with 13C in the methyl group at position 5, was incorporated into unilamellar vesicles of egg phosphatidylcholine. The vesicles are impermeable to the shift reagent Pr3+ and, in the presence of this reagent, separate 13C resonances due to labelled \u3b1-tocopherol in the outer and inner monolayers could be observed with relative intensities, 2:1. Subsequent addition of the relaxation reagent Gd2+ causes broadening and greatly shortened spin-lattice relaxation times for the resonance due to \u3b1-tocopherol in the outer monolayer only. These data confirm that \u3b1-tocopherol is located in both halves of the bilayers with its more hydrophilic chroman moiety very near the lipid-water interface, and indicate that the methyl group at position 5 of the \u3b1-tocopherol in the inner monolayer must be at least 40 \uc5 from the aqueous interface of the outer monolayer. \ua9 1985.Peer reviewed: YesNRC publication: Ye

Skin compatibility of cyclodextrins and their derivatives: a comparative assessment using a corneoxenometry bioassay.

Few studies have been performed to assess the risk of skin damage by cyclodextrins (CD) and they have yielded contradictory results. The present study was conducted using the corneoxenometry bioassay on human stratum corneum to compare the skin compatibility of CD currently used in pharmaceutical preparations (betaCD, gammaCD, Rameb, Dimeb, Trimeb, HP-betaCD and HP-gammaCD) and that of new amphiphilic CD derivatives, namely, the phospholipidyl-CD (DMPE-Dimeb and DMPE-Trimeb). All the tested CD were well tolerated by the stratum corneum at a concentration of 5%. However, inter-individual reactivity was larger for DMPE-Dimeb, suggesting a more aggressive trend for this compound. Cutaneous Index of Mildness values obtained confirm that Dimeb is able to extract some skin components and shows that DMPE-Dimeb performs similarly

Vasoactive intestinal contractor (VIC) peptide structure in solution as determinated by proton NMR

The Vasoactive Intestinal Contractor peptide has been synthesized and studied by 1H NMR in 50/50 acetonitrile/water mixture. All spin systems were identified and assigned with the aid of 2D experiments. Modeling was performed with constraints obtained by NOEs. Some distances used in modeling were calculated from build-up data. Kinetic exchange of the amide protons showed that the 9-15 helical segment is stabilized by at least three hydrogen bonds. The proposed structure is compared with those of Nle-7 endothelin and Sarafotoxin-S6b previously obtained in same conditions