Structure of the nerve myelin membrane: Proof of the low-resolution profile

Abstract

In analyzing the low-angle X-ray diffraction patterns recorded from the normal and swollen my&n in frog sciatic nerve, a precise value is found for the centerto-center distance between the pair of membranes constituting the repeating structure in the myelin. The previously reported large increase in period when the nerve is put in hypotonic Ringer's solution is shown to be accompanied by a small decrease in the center-to-center distance of the membranes within one pair. Thus both a large amplitude swelling at the extracellular interface between membrane pairs and a moderate one at the cytoplasmic interface within the pair are observed. The two kinds of swelling-cytoplasmic and extracellular-are suficient to demonstrate crystallographically the correctness of the bilayer profile for a single myelin membrane. The existence of a lipid bilayer within the membrane iv confirmed by the scale of absolute electron density derived from the swelling experiments, and hydrated surface layers of protein are postulated.

Energetics of Pore Formation Induced by Membrane Active Peptides

“…The magnitude of the diffraction amplitude was the square root of the integrated intensity. The phases were determined by the swelling method (43). With their phases determined, the diffraction amplitudes were Fourier transformed to obtain the transbilayer electron density profiles.…”

“…The abscissa is the X-ray momentum transfer q ) 4π sin θ/λ, where λ is the X-ray wavelength, 1.54 Å. The phases were chosen according to the swelling method (43,45,46). thickness, h, of the bilayer was estimated by subtracting twice the length of the glycerol region (from the phosphate to first methylene of the hydrocarbon chain), that is, ∼10 Å, from PtP (47-51).…”

The structure of a lipid–water lamellar phase containing two types of lipid monolayers. An X-ray and neutron scattering study

“…The two structures are represented in Fig. 2 One drawback of the X-ray scattering study is the very small range in water content in which the phase L7 is stable (the amount of water varies between 10 and 20 °/) which hinders a satisfactory phasing of the reflections by 'swelling' methods (Blaurock, 1971). It seemed to us that in a neutron scattering experiment this problem could be solved more easily by taking advantage of the scattering-amplitude difference between D20 and H20 (Zacca'i, Blasie & Schoenborn, 1975;Worcester, 1976).…”

Direct X-ray determination of the electron-density profile of the nerve myelin membrane, with paracrystalline lattice distortions taken into account

“…5b). With the help of swelling experiments, the cytoplasmic membrane pair, with a centre-to-centre distance of about 71-76 A (Blaurock, 1971) has generally been designated as the unit cell. The analysis here also shows that upon swelling in sucrose and glycerol solutions, the cytoplasmic membrane pair remains together while the extracellular pair parts.…”

“…In previous methods described by various authors for determining the electron density distribution of the double membrane, such as the swelling and sampling methods (Finean & Burge, 1963;Moody, 1963;Blaurock, 1971); fixation techniques tAkers & Parsons, 1970;Harker, 1972); comparison of optic and sciatic myelin systems (Caspar & Kirschner, 1971), application of the direct method of Hosemann & Bagchi (1962) making use of the so-called relaxation deconvolution method (Worthington & McIntosh, 1973, 1974, the influence of distance statistics in the membrane system has generally been neglected.…”