Physical structure of the excitable membrane of unmyelinated axons: x-ray scattering study and electrophysiological properties of pike olfactory nerve 1 1Edited by J. Karn

X-ray Scattering Study of Pike Olfactory Nerve: Intensity of the Axonal Membrane, Solution of the Phase Problem and Electron Density Profile

“…We ascribed the invariant part of the spectra (0.024!s%0.04 Å K1 ) to the axonal membrane itself. 1 The nerve-dependent component, observed below sZ0.024 Å K1 , yielded the information required to discriminate the axonalmembrane spectrum from the non-membrane components. Ridding the spectra of the non-membrane components: thickness and intensity of the axonal membrane…”

“…1 The 1-D spectra analysed in this work were obtained by subtracting the meridional from the equatorial trace of 2-D spectra, 1 an operation aimed at discriminating the spectra of the macromolecular components oriented with respect to the nerve from the intensity originating from the unoriented components. The predominant oriented components are presumably axonal membranes, MT and SDF (see Morphology of pike olfactory nerve, above).…”

“…Yet, a recent synchrotron radiation study of unmyelinated pike olfactory nerves raised some hope that the structure of these membranes might be brought within reach of an X-ray scattering approach. 1 We showed in that work that the scattering spectra of pike olfactory nerve display a diffuse band similar to the spectrum of isolated myelin membranes, accompanied by a few sharper bands reminiscent of microtubules. The analysis of the high-angle region (sO0.022 Å K1 ) of the spectra, where the contribution of the non-membrane components is presumably negligible, showed that membrane thickness decreases as temperature increases, with a thermal expansion coefficient equal to K0.97(G0.19)!10 K3 8C K1 , a typical phenomenon of lipid-containing systems with 0022-2836/$ -see front matter q 2004 Elsevier Ltd. All rights reserved.…”

X-ray Scattering Study of Pike Olfactory Nerve: Elastic, Thermodynamic and Physiological Properties of the Axonal Membrane

“…1 The expression of the intensity scattered by a pair of membranes is trivial when the membranes are centrosymmetric 1 but it deserves some attention if the individual membranes lack a centre of Table 2). Lower frame: two spectra obtained in the presence of drugs.…”

“…2 Another agent was isotonic KCl, whose effects we studied earlier. 1 The novelty of the present work is the evaluation of the energy involved in the thickness dilation process, which is defined by the elastic modulus of area compressibility. We also looked more carefully into the puzzling phenomenon of membrane pairing.…”