Multinuclear and magic-angle spinning NMR investigations of molecular organization in phospholipid-triglyceride aqueous dispersions

Ka Loh Li, Cherryl A. Tihal, Mingming Guo, Ruth E. Stark

    Research output: Contribution to journalArticlepeer-review

    Abstract

    The supramolecular organization of multi-bilayers formed by aqueous egg phosphatidylcholine-triolein (PC-TO) mixtures has been investigated using 31P, 13C, and 1H nuclear magnetic resonance (NMR). For these emulsions, which mimic substrates in the early hydrolytic stages of fat digestion, the NMR spectra obtained with magic-angle spinning (MAS) exhibit resolution comparable to that of sonicated vesicles and integrated peak intensities consistent with their chemical composition. Both 31P line shapes and MAS sideband patterns from the phosphocholine group indicate that mixing with triolein produces a PC bilayer which remains predominantly liquid crystalline in its organization; nevertheless, anomalous spectral features in MAS spectra may be attributed to additional phases in which the headgroups adopt a different orientation with respect to the bilayer normal, and tight packing enhances phosphorus-phosphorus interactions. 13C and 1H line widths monitored as a function of PC mole fraction, spinning speed, and decoupling strength show that the choline headgroups and glycerol backbones are anchored preferentially in the phospholipid-triglyceride assemblies, whereas all acyl chains become very fluid. The average degree of chain order also decreases for the mixed dispersions, as judged from spinning-sideband intensities in 1H MAS NMR spectra. The absence of proton spin-diffusion effects in the PC-TO multilayers is demonstrated by examination of their spinning sidebands and relaxation times, making it possible to use MAS-assisted two-dimensional NMR to assign overlapped 1H resonances and to identify proximal interactions between the two constituents. The usefulness of these NMR strategies in mechanistic studies of gastric fat digestion is also discussed. © 1993 American Chemical Society.
    Original languageEnglish
    Pages (from-to)9926-9935
    Number of pages9
    JournalBiochemistry
    Volume32
    Issue number38
    Publication statusPublished - 1993

    Keywords

    • Carbon Isotopes
    • Hydrogen
    • *Lipid Bilayers
    • Magnetic Resonance Spectroscopy/methods
    • Models, Biological
    • Molecular Conformation
    • Phosphatidylcholines/*chemistry
    • Phosphorus
    • Support, U.S. Gov't, P.H.S.
    • Triolein/*chemistry

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