Lipid organization in peripheral nerve: Natural abundance carbon-13 NMR spectroscopy on intact tissues

Native structures of peripheral nerve myelin can directly be observed by carbon-13 nuclear magnetic resonance (NMR) spectroscopy after dissecting epineurial and perineurial tissue sheaths from the endoneurium. NMR spectra of the intact endoneurial tissue describe a highly ordered and largely immobilized lipid phase in the myelin membrane which is in marked contrast to the fluid-like lipid distribution in the intracellular lipid droplets of epineurium and perineurium. Membrane reconstitution experiments with total endoneurial lipids, but without protein, suggest a primary role of the lipids in myelin bilayer assembly. Reconstitution experiments also indicate that polar lipid-protein interactions in native myelin involve the CH₂-N function of choline phospholipids, in particular.