scholarly journals ELECTRON MICROSCOPE AND X-RAY DIFFRACTION STUDIES OF THE EFFECTS OF DEHYDRATION ON THE STRUCTURE OF NERVE MYELIN

1960 ◽  
Vol 8 (1) ◽  
pp. 13-29 ◽  
Author(s):  
J. B. Finean
Keyword(s):  
Electron Microscope ◽  
Electron Micrographs ◽  
Diffraction Data ◽  
Intermediate Stage ◽  
X Ray Diffraction ◽  
X Ray ◽  
Dense Line ◽  
Tissue Shrinkage ◽  
Frog Sciatic Nerve ◽  
Electron Microscope Data

The dehydration of frog sciatic nerve has been studied by allowing specimens to become partially or fully dried before fixation and preparation for electron microscopy. Low magnification electron micrographs of OsO4-fixed preparations showed marked tissue shrinkage which could be correlated quantitatively with the loss of water during the preliminary drying. KMnO4-fixation appeared to cause a rehydration of the dried tissue. Higher magnification electron micrographs of the OsO4-fixed preparations showed a sequence of modifications of the myelin layers which could be correlated with changes in the small-angle x-ray diffraction data which were recorded during drying. An intermediate stage of drying was characterised by a partial collapse of layers and a disappearance of the intraperiod dense line in some regions of the myelin sheath. Continuity between collapsed and non-collapsed layers was maintained throughout the sheath. The fully dried preparation showed two main modifications of the myelin layers. In many regions the layers (principal layers) resembled those of normal preparations, but showed an intensification and frequently a doubling of the intraperiod dense line. In addition, there was a very extensive system of fine (40 A periodicity) dense layers, some of which could be demonstrated to be continuous with the principal layers. In such cases it was observed that two of the fine layers were related to each principal layer. The correlation between diffraction data and electron microscope data is discussed, and some speculations are made concerning the molecular significance of the observations.

scholarly journals SEQUENCES IN THE FORMATION OF CLOTS FROM PURIFIED BOVINE FIBRINOGEN AND THROMBIN: A STUDY WITH THE ELECTRON MICROSCOPE

1949 ◽  
Vol 90 (3) ◽  
pp. 225-232 ◽  
Author(s):  
Keith R. Porter ◽  
Clinton Van Zandt Hawn
Keyword(s):  
Electron Microscope ◽  
Electron Micrographs ◽  
X Ray Diffraction ◽  
X Ray ◽  
Physical Constants ◽  
Lateral Association ◽  
Fibrinogen Molecule

The observed sequences in the formation of clots from purified bovine fibrinogen and thrombin are described. Under the conditions of these experiments, it appears that fibrinogen molecules are polymerized by the action of thrombin to form needle-shaped, crystal-like protofibrils which then become aligned into fiber strands by lateral association. The integrity of the unit fibrils is maintained within the strand. A model of the fibrinogen molecule is proposed which may satisfy the reported physical constants, data from x-ray diffraction studies, and observations made upon electron micrographs.

Scanning Electron Microscope Studies on the Morphology of Zeolites Occurring in Bentonites

1974 ◽  
Vol 32 ◽  
pp. 458-459
Author(s):  
Paul J. Jehn ◽  
Necip Güven ◽  
J. Franklin Bailey
Keyword(s):  
Electron Microscope ◽  
Scanning Electron Microscope ◽  
Diffraction Data ◽  
X Ray Diffraction ◽  
X Ray ◽  
Volcanic Material ◽  
Scanning Electron

Zeolites occur as major constituents in several bentonite samples from Japan and Argentina. They are believed to be formed by devitrification of volcanic material. X-ray diffraction data indicate that the major zeolite phases in these samples are heulandite Ca(Al2Si7O18)·6H2O, clinoptilolite Na2(Al2Si7O18)6H2O, mordenite (Na2K2Ca) (Al2Si10O24)·7H2O, analcite Na(AlSi2O6)·H2O and possibly epistilbite Ca(Al2Si6O16)·5H2O.

scholarly journals Gap junction structures: Analysis of the x-ray diffraction data

1977 ◽  
Vol 74 (2) ◽  
pp. 629-645 ◽  
Author(s):  
L Makowski ◽  
DLD Caspar ◽  
WC Phillips ◽  
DA Goodenough
Keyword(s):  
Electron Microscope ◽  
Gap Junction ◽  
Electron Density ◽  
Diffraction Data ◽  
Pair Correlation ◽  
Hexagonal Lattice ◽  
Chemical Data ◽  
X Ray Diffraction ◽  
Interference Function ◽  
X Ray

Models for the spatial distribution of protein, lipid and water in gap junction structures have been constructed from the results of the analysis of X-ray diffraction data described here and the electron microscope and chemical data presented in the preceding paper (Caspar, D. L. D., D. A. Goodenough, L. Makowski, and W.C. Phillips. 1977. 74:605-628). The continuous intensity distribution on the meridian of the X-ray diffraction pattern was measured, and corrected for the effects of the partially ordered stacking and partial orientation of the junctions in the X-ray specimens. The electron density distribution in the direction perpendicular to the plane of the junction was calculated from the meridional intensity data. Determination of the interference function for the stacking of the junctions improved the accuracy of the electron density profile. The pair-correlation function, which provides information about the packing of junctions in the specimen, was calculated from the interference function. The intensities of the hexagonal lattice reflections on the equator of the X-ray pattern were used in coordination with the electron microscope data to calculate to the two-dimensional electron density projection onto the plane of the membrane. Differences in the structure of the connexons as seen in the meridional profile and equatorial projections were shown to be correlated to changes in lattice constant. The parts of the junction structure which are variable have been distinguished from the invariant parts by comparison of the X-ray data from different specimens. The combination of these results with electron microscope and chemical data provides low resolution three- dimensional representations of the structures of gap junctions.

scholarly journals ELECTRON MICROSCOPE AND LOW-ANGLE X-RAY DIFFRACTION STUDIES OF THE NERVE MYELIN SHEATH

1957 ◽  
Vol 3 (5) ◽  
pp. 725-748 ◽  
Author(s):  
H. Fernández-morán ◽  
J. B. Finean
Keyword(s):  
Electron Microscopy ◽  
Electron Microscope ◽  
Electron Micrographs ◽  
Myelin Sheath ◽  
High Resolution Electron Microscopy ◽  
Molecular Organization ◽  
X Ray Diffraction ◽  
Freezing And Thawing ◽  
X Ray ◽  
Myelin Structure

1. A close correlation has been obtained between high resolution electron microscopy and low-angle x-ray diffraction studies of the myelin sheath of frog and rat peripheral and central nerves. Extensive studies were performed by application of both techniques to the same specimens, prepared for examination by OsO4 or KMnO4 fixation, and embedding either in methacrylate or in gelatin employing a new procedure. Controlled physical and chemical modifications of the myelin sheath prior to fixation were also investigated. 2. A correspondence was established between the layer spacings observed in electron micrographs and the fundamental radial repeating unit indicated by the low-angle x-ray diffraction patterns. The variations in relative intensities of the low-angle x-ray reflections could be related to the radial density distributions seen in the electron micrographs. 3. An analysis of the preparation procedures revealed that OsO4 fixation introduces a greater shrinkage of the layer spacings and more pronounced changes in the density distribution within the layers than KMnO4 fixation. The effects of methacrylate and gelatin embedding are described, and their relative merits considered in relation to the preservation of myelin structure by OsO4 fixation. 4. The experimental modifications introduced by freezing and thawing of fresh whole nerve are described, particularly the enhancement of the intermediate lines and the dissociation of the layer components in the myelin sheath. A characteristic collapsing of the radial period of the sheath is observed after subjecting fresh nerve trunks to prolonged and intense ultracentrifugation. 5. Controlled extraction of fresh nerve with acetone at 0°C., which preferentially removes cholesterol, produces characteristic, differentiated modifications of the myelin sheath structure. Electron microscopy reveals several types of modifications within a single preparation, including both expanded and collapsed layer systems, and internal rearrangements of the layer components. Alcohol extraction leads to a more extensive structural breakdown, but in certain areas collapsed layer systems can still be observed. The components of the lipide extracts could be identified by means of x-ray diffraction. These modifications emphasize the importance of cholesterol in the myelin structure, and disclose a resistance of the dense osmiophilic lines to lipide solvents. 6. The significance of these structures is discussed in relation to present concepts of the molecular organization of myelin. The available evidence is consistent with the suggestion that the primary site of osmium deposition is at the lipoprotein interfaces and that the light bands probably represent regions occupied by lipide chains. The electron microscope and x-ray diffraction data also indicate the possibility of a regular organization within the plane of the layers, probably involving units of 60 to 80 A. The myelin sheath is regarded as a favourable cell membrane model for detailed analysis by combined application of x-ray diffraction and electron microscopy.

scholarly journals ELECTRON MICROSCOPE AND X-RAY DIFFRACTION STUDIES OF THE EFFECTS OF DEHYDRATION ON THE STRUCTURE OF NERVE MYELIN

1960 ◽  
Vol 8 (1) ◽  
pp. 31-37 ◽  
Author(s):  
J. B. Finean
Keyword(s):  
Electron Microscopy ◽  
Electron Microscope ◽  
Optic Nerve ◽  
Sciatic Nerve ◽  
Small Angle ◽  
Striking Difference ◽  
X Ray Diffraction ◽  
X Ray ◽  
Diffraction Patterns ◽  
Frog Sciatic Nerve

The dehydration of rat optic nerve has been studied by allowing specimens to become partially or fully dried before fixation and preparation for electron microscopy. A correlation is established between electron micrographs of the myelin sheath and corresponding small-angle x-ray diffraction patterns. The modifications of the optic nerve myelin layers during drying were very similar to those described in more detail for the myelin of frog sciatic nerve. The most striking difference was that the system of fine layers characteristic of the fully dried myelin was much more extensive in the case of the optic nerve, and the layer thickness was significantly greater than the corresponding layer in the frog sciatic nerve preparation. The significance of these correlations is discussed.

PENGGUNAAN TiO2 PARTIKEL NANO HASIL SINTESIS BERBASIS AIR MENGGUNAKAN METODA SOL-GEL PADA BAHAN KAPAS SEBAGAI APLIKASI UNTUK TEKSTIL ANTI UV

Arena Tekstil ◽  
2013 ◽  
Vol 28 (1) ◽  
Author(s):  
Maya Komalasari ◽  
Bambang Sunendar
Keyword(s):  
Fourier Transform ◽  
Electron Microscope ◽  
Scanning Electron Microscope ◽  
Sol Gel ◽  
Crosslinking Agent ◽  
X Ray Diffraction ◽  
Nano Tio2 ◽  
X Ray ◽  
Infra Red ◽  
Scanning Electron

Partikel nano TiO2 berbasis air dengan pH basa telah berhasil disintesis dengan menggunakan metode sol-gel dan diimobilisasi pada kain kapas dengan menggunakan kitosan sebagai zat pengikat silang. Sintesis dilakukan  dengan prekursor TiCl4 pada konsentrasi 0,3 M, 0,5 M dan 1 M, dan menggunakan templat kanji dengan proses kalsinasi pada suhu 500˚C selama 2 jam. Partikel nano TiO2 diaplikasikan ke kain kapas dengan metoda pad-dry-cure dan menggunakan kitosan sebagai crosslinking agent. Berdasarkan hasil Scanning Electron Microscope (SEM),diketahui bahwa morfologi partikel TiO2 berbentuk spherical dengan ukuran nano (kurang dari 100 nm). Karakterisasi X-Ray Diffraction (XRD) menunjukkan adanya tiga tipe struktur kristal utama, yaitu (100), (101) dan (102) dengan fasa kristal yang terbentuk adalah anatase dan rutile. Pada karakterisasi menggunakan SEM terhadap serbuk dari TiO2 yang telah diaplikasikan ke permukaan kain kapas, terlihat adanya imobilisasi partikel nano TiO2 melalui ikatan hidrogen silang dengan kitosan pada kain kapas. Hasil analisa tersebut kemudian dikonfirmasi dengan FTIR (Fourier Transform Infra Red) yang hasilnya memperlihatkan puncak serapan pada bilangan gelombang 3495 cm-1, 2546 cm-1, dan 511 cm-1,  yang masing-masing diasumsikan sebagai adanya vibrasi gugus fungsi O-H, N-H dan Ti-O-Ti. Hasil SEM menunjukkan pula bahwa kristal nano yang terbentuk diantaranya adalah fasa rutile , yang berdasarkan literatur terbukti dapatberfungsi sebagai anti UV.

scholarly journals High-pressure synthesis and crystal structure of the mixed-cation borate Ga4In4B15O33(OH)3

2019 ◽  
Vol 74 (4) ◽  
pp. 357-363
Author(s):  
Daniela Vitzthum ◽  
Hubert Huppertz
Keyword(s):  
Crystal Structure ◽  
High Pressure ◽  
High Temperature ◽  
Diffraction Data ◽  
X Ray Diffraction ◽  
Synthesis And Crystal Structure ◽  
X Ray ◽  
Mixed Cation ◽  
High Pressure High Temperature ◽  
Pressure Synthesis

AbstractThe mixed cation triel borate Ga4In4B15O33(OH)3 was synthesized in a Walker-type multianvil apparatus at high-pressure/high-temperature conditions of 12.5 GPa and 1300°C. Although the product could not be reproduced in further experiments, its crystal structure could be reliably determined via single-crystal X-ray diffraction data. Ga4In4B15O33(OH)3 crystallizes in the tetragonal space group I41/a (origin choice 2) with the lattice parameters a = 11.382(2), c = 15.244(2) Å, and V = 1974.9(4) Å3. The structure of the quaternary triel borate consists of a complex network of BO4 tetrahedra, edge-sharing InO6 octahedra in dinuclear units, and very dense edge-sharing GaO6 octahedra in tetranuclear units.

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