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

Gbordzoe, M.K.; Kreutz, W.

doi:10.1107/s0021889878013692

Cited by 3 publications

(1 citation statement)

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“…Such a refinement for fitting an entire intensity distribution has been successfully used for the analysis of powder patterns (Young et al, 1980;Wiles and Young, 1981) and for biological membranes (Funk et al, 1981). A least squares procedure has also been applied to the generalized Patterson function (Q-function) of biological membranes including nerve myelin (Pape et al, 1977;Gbordzoe and Kreutz, 1978). In the present work we found that the least squares procedure allowed us to optimize the parameters after relatively few…”

Section: Analysis Of Myelin Diffraction Patternsmentioning

confidence: 77%

Membrane structure in isolated and intact myelins

Inouye

Karthigasan

Kirschner

1989

Biophysical Journal

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The biochemical composition of myelin and the topology of its constituent lipids and proteins are typically studied using membranes that have been isolated from whole, intact tissue using procedures involving hypotonic shock and sucrose density gradient centrifugation. To what extent, however, are the structure and intermembrane interactions of isolated myelin similar to those of intact myelin? We have previously reported that intact and isolated myelins do not always show identical myelin periods, indicating a difference in membrane-membrane interactions. The present study addresses the possibility that this is due to altered membrane structure. Because x-ray scattering from isolated myelin sometimes consists of overlapping Bragg reflections or is continuous, we developed nonlinear least squares procedures for analyzing the total intensity distribution after film scaling, background subtraction, and Lorentz correction. We calculated electron density profiles of isolated myelin for comparison with membrane profiles from intact myelin. The change in the width of the extracellular space and the relative invariance of the cytoplasmic space as a function of pH and ionic strength that we previously found for intact nerve was largely paralleled by isolated myelin. There were two exceptions: isolated CNS myelin was resistant to swelling under all conditions, and isolated PNS myelin in hypotonic saline showed indefinite swelling at the extracellular apposition. However, electron density profiles of isolated myelins, calculated to 30 A resolution, did not show any major change in structure compared with intact myelin that could account for the differences in interactions.

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